[gnome-control-center] (18 commits) Non-fast-forward update to branch wip/jsparber/background

[Julian Sparber <jsparber src gnome org>]

The branch 'wip/jsparber/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:

  8a5150e... background: resize preview when the window size is less the
  d321074... background: add slide icon to time changing wallpapers
  2647a82... background: change margins for preview to 16px
  219c416... background: change size of preview when panel is heigher th
  47d87f8... background: expand thumbnails to fill a gallery row
  4471b20... background: add icon for with time changing wallpapers
  917f219... background: moved gallery item code to grid-item class
  4c04af9... background: add white space around gallery and min/max per 
  8113f18... background: set wallpaper and lockscreen
  3a93057... background: clean up code
  6bd2135... background: refactor cc-background-store
  fbc0cc9... background: make cc_background_grid_item_set_ref static and
  3ccf4e9... background: change name cc_background_grid_item_get_ref
  9f922ab... background: less exposure of the the wallpaper store
  fdbc19d... background: change base obj of CcBackgroundGridItem
  ce0ec1e... background: CcBackgroundGridItem::new returns its own typ
  81ccda3... background: cache tumbnail for wallpaper gallery for a redr
  3601466... background: changed variable names and small style changes
  44d3509... background: cache slideshow-emblem icon
  4c792d0... background: show only top border for gallery view
  4f3d8c9... background: adapt meson.build for file changes
  2237a0c... background: change description for open in File and open in
  cd3a71c... background: fix crash of g-c-c by opening gnome-photos
  88024ef... background: use autoptr where possible
  2a9a1d5... background: clean up files and code and remove build warnin

Commits added to the branch:

  cdcb3e4... background: resize preview based on window size
  633d766... background: set wallpaper and lockscreen
  999a3a3... background: clean up code
  a163882... background: refactor cc-background-store
  00f92d6... background: make cc_background_grid_item_set_ref static and
  2178ac1... background: change name cc_background_grid_item_get_ref
  8da29a8... background: less exposure of the the wallpaper store
  ff8a8be... background: change base obj of CcBackgroundGridItem
  600054f... background: CcBackgroundGridItem::new returns its own typ
  0b78eaf... background: cache tumbnail for wallpaper gallery for a redr
  809e1c0... background: changed variable names and small style changes
  9aebc85... background: cache slideshow-emblem icon
  325b053... background: show only top border for gallery view
  e6e9c27... background: adapt meson.build for file changes
  5d9a897... background: change description for open in File and open in
  5f9792c... background: fix crash of g-c-c by opening gnome-photos
  370b09e... background: use autoptr where possible
  d5dedd2... background: clean up files and code and remove build warnin