Adds Date Time panel to the system panel as a page. https://gitlab.gnome.org/Teams/Design/settings-mockups/-/blob/master/system/system-panel.png See #2241
Recent versions of Gettext are able to translate several formats that are used in GNOME applications. This patch migrates from Intltool to Gettext by using meson's i18n features. https://bugzilla.gnome.org/show_bug.cgi?id=787588
https://bugzilla.gnome.org/show_bug.cgi?id=658352