Add an extra button "Clean Print Heads" that will be shown when the relevant
maintenance command is available for a printer, to bring this feature back.
Additionally, this commit adds a 'parameters' attribute to PpMaintenanceCommand,
which is needed as the "Clean" command requires to at least be passed "all" as
its single parameter: https://www.cups.org/doc/spec-command.html#Cleanhttps://bugzilla.gnome.org/show_bug.cgi?id=764620
Set 'PageSize' instead of 'media' for new printers since we use PPD
for construction of the combo for selecting of default paper size.
Previously, we've been setting 'media' attribute for new printers.
Attribute 'media' is used by IPP but we set paper size using 'PageSize'
which comes from PPD in the options dialog. Sometimes (quite often) IPP
gets priority over PPD in print systems. Therefore there was inconsistency
of what user set as default paper size on the options dialog and what was used.
Also don't mark IPP and user's local options as default in PpPPDOptionWidget
since it should use just PPD (we can change PPD values only in this widget).
Since we use PPD for setting of paper size in the options dialog, we shouldn't
show a value which user does not change actually (IPP's 'media' vs. PPD's
'PageSize').
https://bugzilla.gnome.org/show_bug.cgi?id=748569
PpNewPrinter contains asynchronous method for installation of
new printer. The new printer is specified by given parameters (e.g. name,
device-id, device-uri, ppd-name, info, location, ...). (#683229)
