Settings: Custom lock screen background [2/2]

Patch Set 1:    * port the custom lock screen feature from
                  ics (http://review.cyanogenmod.org/#/c/16914)

Patch Set 2:    * rename some strings
                * use constants instead of numbers
                * fix some code styling issues

Patch Set 3:    * code cleanup

Patch Set 4:    * rebased

Patch Set 5-6:  * code cleanup

Patch Set 7:    * fix comment location

Change-Id: Ib00d84c25016094537bac37843b2dcdc3c6200f3

Conflicts:

	res/values/arrays.xml
	src/com/aokp/romcontrol/fragments/UserInterface.java