Lockscreen custom wallpaper && lockscreen style options (2/2)

  - Color Fill
  - Custom Wallpaper
  - Default background
  - Alpha slider in color fill
merged http://review.gummyrom.com/#/c/1226/4

Change-Id: I6d695101c1f4468a0df6d4c3a4a907cc272401ab
Update ColorPicker powered by SlimRom

Change-Id: I48e7c8a535c6ac2da02470fd087443b0ab757328