Fix: wallpaper changes when changing lockscreen WP

Since LockscreenWallpaperPickerActivity did not override
cropImageAndSetWallpaper the homescreen wallpaper was changing
when selecting the default_wallpaper resource.

Change-Id: I26dd28e628a3ef701ad92a81aa80327d3ccba092
Add navbar background preview to ThemesContract

Change-Id: Id3ed43c86649b1757fec7f3fc7dee2d2730258e2