[gnome-control-center] (19 commits) Non-fast-forward update to branch gbsneto/background

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

The branch 'gbsneto/background' 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:

  8ecf2e0... flatpak: Add gnome-backgrounds
  8e87358... background: Rename ui file to cc-background-panel.ui
  da7e0fc... background: Turn into a template class
  4d43a92... background: Make BgSource receive a GtkWidget
  1725547... background: Introduce CcBackgroundChooser
  d24f05e... background-panel: Remove background chooser buttons
  5ec0037... background: Cache thumbnails in CcBackgroundItem
  59da75e... background: Switch to GtkFlowBox
  d293047... background: Remove CcBackgroundChooserDialog
  a111919... background: Use the cairo_t provided by GTK
  96b4d18... background: Move preview to CcBackgroundPreview
  08e5d36... background: Use widgets to render slideshow emblem
  f68117d... background: Introduce BgRecentSource
  43b80a7... background: Add recent backgrounds
  36cecde... background: Add "Open Picture..." header button
  d69f688... background: Remove dead code

Commits added to the branch:

  f972ffc... keyboard: Clarify that mute key toggles the mute state (*)
  936a66f... keyboard: Add microphone mute key (*)
  e2f5668... flatpak: Add gnome-backgrounds
  c290dad... background: Rename ui file to cc-background-panel.ui
  ad740de... background: Turn into a template class
  5afc292... background: Make BgSource receive a GtkWidget
  2f032f2... background: Introduce CcBackgroundChooser
  df80d4a... background-panel: Remove background chooser buttons
  ee37d01... background: Cache thumbnails in CcBackgroundItem
  c64ab47... background: Switch to GtkFlowBox
  214f037... background: Remove CcBackgroundChooserDialog
  205bfb9... background: Use the cairo_t provided by GTK
  5b21440... background: Move preview to CcBackgroundPreview
  5ba721b... background: Use widgets to render slideshow emblem
  9e39748... background: Introduce BgRecentSource
  6c5270d... background: Add recent backgrounds
  728d3b4... background: Add "Open Picture…" header button
  6df2b0b... background: Remove dead code
  8d9ed8c... background: Cleanup BgColorsSource

(*) This commit already existed in another branch; no separate mail sent