Settings : Lockscreen background customization (2/2)

Allow user to customize lockscreen background (port from cm7)

Patchset 2 : Remove default button from color dialog
Patchset 3 : Update strings according to request
Patchset 4 : String cleanup
             Switch to png
Patchset 5 : Summary cleanup
             ColorPicker value check
Patchset 6 : Shorten preference title
             Move preference up
Patchset 7 : Restore consumed newline

Change-Id: I104382548dcb64db52a06e24922687fbae1e32a8

Conflicts:
	res/values/arrays.xml
	src/com/android/settings/cyanogenmod/LockscreenInterface.java