Add back setting that was removed from last commit.
Settings: customizable slim lockscreen background (2/2)

- color fill (with transparency slider)
- custom image  (with transparency slider)
- full transparent
- default

This Settingspart containes a small comment change for Notificationbackground settings

Patchset 2: cleanup

Change-Id: I6542dd72b02a9fcdbf1159fa95ba64fcfc75796e

Conflicts:
	res/values/arrays.xml
	res/values/strings.xml
	res/xml/lockscreen_interface_settings.xml
	src/com/android/settings/slim/LockscreenInterface.java
	src/com/android/settings/slim/NotificationDrawerSettings.java