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: I35e5c70fff423770a03b5bb39d439ebea82dd56a

Conflicts:
	res/values/arrays.xml
	res/values/strings.xml
	src/com/android/settings/cyanogenmod/LockscreenInterface.java
TouchInterceptor: Fixed image cache problems
Fixes the problem shown in this video:
http://youtu.be/piqHych4nJY

Change-Id: I42f35ddd6677afd10187a7c5a390287acd3f39a9
Settings: Make it clearer how SMS Limiting works and add 500 messages option

Change-Id: Ia7458d7e7cde1cfbb6641d4b05fd9caf59d21db8