CI: AppImage support

- Add a script for building a Calamares AppImage file (this is
   useful in *some* limited contexts, not a general way to distribute
   Calamares since it's much more efficient to use installed libs).
 - Add example config files for this AppImage build.
 - Download the linuxdeploy tools if they are missing
 - Document script flags some more

data/config-appimage/modules/displaymanager.conf

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+# Configure one or more display managers (e.g. SDDM)
+# with a "best effort" approach.
+---
+#The DM module attempts to set up all the DMs found in this list, in that precise order.
+#It also sets up autologin, if the feature is enabled in globalstorage.
+#The displaymanagers list can also be set in globalstorage, and in that case it overrides anything set up here.
+displaymanagers:
+  - slim
+  - sddm
+  - lightdm
+  - gdm
+  - mdm
+  - lxdm
+  - kdm
+
+#Enable the following settings to force a desktop environment in your displaymanager configuration file:
+#defaultDesktopEnvironment:
+#    executable: "startkde"
+#    desktopFile: "plasma"
+
+#If true, try to ensure that the user, group, /var directory etc. for the
+#display manager are set up correctly. This is normally done by the distribution
+#packages, and best left to them. Therefore, it is disabled by default.
+basicSetup: false
+
+#If true, setup autologin for openSUSE. This only makes sense on openSUSE
+#derivatives or other systems where /etc/sysconfig/displaymanager exists.
+sysconfigSetup: false

data/config-appimage/modules/finished.conf

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+# Configuration for the "finished" page, which is usually shown only at
+# the end of the installation (successful or not).
+---
+# The finished page can hold a "restart system now" checkbox.
+# If this is false, no checkbox is shown and the system is not restarted
+# when Calamares exits.
+restartNowEnabled: true
+
+# Initial state of the checkbox "restart now". Only relevant when the
+# checkbox is shown by restartNowEnabled.
+restartNowChecked: false
+
+# If the checkbox is shown, and the checkbox is checked, then when
+# Calamares exits from the finished-page it will run this command.
+# If not set, falls back to "shutdown -r now".
+restartNowCommand: "systemctl -i reboot"
+
+# When the last page is (successfully) reached, send a DBus notification
+# to the desktop that the installation is done. This works only if the
+# user as whom Calamares is run, can reach the regular desktop session bus.
+notifyOnFinished: false

data/config-appimage/modules/keyboard.conf

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+# NOTE: you must have ckbcomp installed and runnable
+#       on the live system, for keyboard layout previews.
+---
+# The name of the file to write X11 keyboard settings to
+# The default value is the name used by upstream systemd-localed.
+# Relative paths are assumed to be relative to /etc/X11/xorg.conf.d
+xOrgConfFileName: "/etc/X11/xorg.conf.d/00-keyboard.conf"
+
+# The path to search for keymaps converted from X11 to kbd format
+# Leave this empty if the setting does not make sense on your distribution.
+convertedKeymapPath: "/lib/kbd/keymaps/xkb"
+
+# Write keymap configuration to /etc/default/keyboard, usually
+# found on Debian-related systems.
+# Defaults to true if nothing is set.
+#writeEtcDefaultKeyboard:   true

data/config-appimage/modules/locale.conf

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+---
+# This settings are used to set your default system time zone.
+# Time zones are usually located under /usr/share/zoneinfo and
+# provided by the 'tzdata' package of your Distribution.
+#
+# Distributions using systemd can list available
+# time zones by using the timedatectl command.
+#    timedatectl list-timezones
+#
+# The starting timezone (e.g. the pin-on-the-map) when entering
+# the locale page can be set through keys *region* and *zone*.
+# If either is not set, defaults to America/New_York.
+#
+region:                     "Europe"
+zone:                       "Amsterdam"
+
+
+# Enable only when your Distribution is using an
+# custom path for locale.gen
+#localeGenPath:             "PATH_TO/locale.gen"
+
+# GeoIP based Language settings:
+#
+# GeoIP need an working Internet connection.
+#
+geoipUrl:                  "https://geoip.kde.org/v1/calamares"
+
+# GeoIP style. Leave commented out for the "legacy" interpretation.
+# This setting only makes sense if geoipUrl is set, enabliing geoIP.
+geoipStyle:    "json"
+

data/config-appimage/modules/users.conf

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+# Configuration for the one-user-system user module.
+#
+# Besides these settings, the user module also places the following
+# keys into the globalconfig area, based on user input in the view step.
+#
+# - hostname
+# - username
+# - password (obscured)
+# - autologinUser (if enabled, set to username)
+#
+# These globalconfig keys are set when the jobs for this module
+# are created.
+---
+# Used as default groups for the created user.
+# Adjust to your Distribution defaults.
+defaultGroups:
+    - users
+    - lp
+    - video
+    - network
+    - storage
+    - wheel
+    - audio
+
+# Some Distributions require a 'autologin' group for the user.
+# Autologin causes a user to become automatically logged in to
+# the desktop environment on boot.
+# Disable when your Distribution does not require such a group.
+autologinGroup:  autologin
+# You can control the initial state for the 'autologin checkbox' in UsersViewStep here.
+# Possible values are: true to enable or false to disable the checkbox by default
+doAutologin:     true
+
+# When set to a non-empty string, Calamares creates a sudoers file for the user.
+#  /etc/sudoers.d/10-installer
+# Remember to add sudoersGroup to defaultGroups.
+#
+# If your Distribution already sets up a group of sudoers in its packaging,
+# remove this setting (delete or comment out the line below). Otherwise,
+# the setting will be duplicated in the /etc/sudoers.d/10-installer file,
+# potentially confusing users.
+sudoersGroup:    wheel
+
+# Setting this to false , causes the root account to be disabled.
+setRootPassword: true
+# You can control the initial state for the 'root password checkbox' in UsersViewStep here.
+# Possible values are: true to enable or false to disable the checkbox by default.
+# When enabled the user password is used for the root account too.
+# NOTE: doReusePassword requires setRootPassword to be enabled.
+doReusePassword: true
+
+# These are optional password-requirements that a distro can enforce
+# on the user. The values given in this sample file disable each check,
+# as if the check was not listed at all.
+passwordRequirements:
+    minLength: -1  # Password at least this many characters
+    maxLength: -1  # Password at most this many characters
+    libpwquality:
+        - minlen=0
+        - minclass=0
+
+userShell: /bin/bash

data/config-appimage/modules/welcome.conf

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+# Configuration for the welcome module. The welcome page
+# displays some information from the branding file.
+# Which parts it displays can be configured through
+# the show* variables.
+#
+# In addition to displaying the welcome page, this module
+# can check requirements for installation.
+---
+# Display settings for various buttons on the welcome page.
+showSupportUrl:         true
+showKnownIssuesUrl:     true
+showReleaseNotesUrl:    true
+
+# Requirements checking. These are general, generic, things
+# that are checked. They may not match with the actual requirements
+# imposed by other modules in the system.
+requirements:
+    # Amount of available disk, in GB. Floating-point is allowed here.
+    # Note that this does not account for *usable* disk, so it is possible
+    # to pass this requirement, yet have no space to install to.
+    requiredStorage:    5.5
+
+    # Amount of available RAM, in GB. Floating-point is allowed here.
+    requiredRam:        1.0
+
+    # To check for internet connectivity, Calamares does a HTTP GET
+    # on this URL; on success (e.g. HTTP code 200) internet is OK.
+    internetCheckUrl:   http://google.com
+
+    # List conditions to check. Each listed condition will be
+    # probed in some way, and yields true or false according to
+    # the host system satisfying the condition.
+    #
+    # This sample file lists all the conditions that are known.
+    check:
+        - ram
+        - power
+        - internet
+        - root
+        - screen
+    # List conditions that **must** be satisfied (from the list
+    # of conditions, above) for installation to proceed.
+    # If any of these conditions are not met, the user cannot
+    # continue past the welcome page.
+    required:
+        - ram

data/config-appimage/settings.conf

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+# Configuration file for Calamares
+# Syntax is YAML 1.2
+---
+modules-search: [ usr/lib/calamares/modules ]
+
+# YAML: list of maps of string:string key-value pairs.
+#instances:
+#- id:       owncloud
+#  module:   webview
+#  config:   owncloud.conf
+
+# Sequence section. This section describes the sequence of modules, both
+# viewmodules and jobmodules, as they should appear and/or run.
+sequence:
+- show:
+  - welcome
+  - locale
+  - keyboard
+  - users
+  - summary
+- exec:
+  - locale
+  - keyboard
+  - users
+  - displaymanager
+  - networkcfg
+- show:
+  - finished
+
+branding: default
+
+prompt-install: false
+# OEM mode
+dont-chroot: true
+disable-cancel: false