[UIFe] Optional (hidden by default) communitheme snap session

[Didier Roche-Tolomelli]

This session isn't displayed and available in GDM by default.

If the communitheme snap is installed, 2 new session options appears, selecting the corresponding theme (for GNOME Shell, sound, GTK2&3, cursor). All session/theme assets will be in the snap. We only expose here default gsettings settings, session files and extension override.

There are 2 new strings for GDM:
* Ubuntu with communitheme snap
* Ubuntu with communitheme snap on Wayland

This is to give the community a chance to get an easy glimpse of our next default theme, backed by the community.
This doesn't impact any default UI has nothing will appear before you install the snap.

[Launchpad Janitor (janitor)]

This bug was fixed in the package ubuntu-settings - 18.04

---------------
ubuntu-settings (18.04) bionic; urgency=medium

  * Add gsettings override for communitheme session (LP: #1760049)

 -- Didier Roche <email address hidden> Fri, 30 Mar 2018 17:29:10 +0200

[Launchpad Janitor (janitor)]

This bug was fixed in the package gnome-session - 3.28.0-0ubuntu2

---------------
gnome-session (3.28.0-0ubuntu2) bionic; urgency=medium

  * Add new communitheme session to the ubuntu session package. This
    session only appears if the communitheme snap is installed. (LP: #1760049)
    - debian/patches/50_ubuntu_sessions.patch, debian/ubuntu-session.install:
      generate and install session file.
    - add Recommends on gtk adwaita and pixbuf theme engine.
    - debian/rules: enable communitheme to override the default ubuntu-dock
      stylesheet from the snap.
    - debian/rules: workaround for Xorg to pick up communitheme cursor theme
      from the snap.
  * Refresh debian/patches/revert_remove_gnome_session_properties.patch

 -- Didier Roche <email address hidden> Fri, 30 Mar 2018 11:03:17 +0200