[gnome-control-center] (7 commits) Non-fast-forward update to branch wip/exalm/appearance

[Alexander Mikhaylenko <alexm src gnome org>]

The branch 'wip/exalm/appearance' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  2ef5321... ua: Use the new high contrast key
  f5fd9f9... ua: Stop setting high contrast WM theme
  5bef9a4... background: Redo the layout to match the new mockups
  0b953b9... background: Add a light/dark style switcher
  55afd9b... background: Rename to Appearance
  729b704... background: Clean up the slideshow icon
  4be2817... background: Polish wallpaper thumbnails

Commits added to the branch:

  7f21270... ua: Use the new high contrast key
  eae6aa4... ua: Stop setting high contrast WM theme
  d72b0d7... background: Redo the layout to match the new mockups
  999762e... background: Add a light/dark style switcher
  3625cf3... background: Rename to Appearance
  4b121ea... background: Clean up the slideshow icon
  9d94040... background: Polish wallpaper thumbnails