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:    * Cleanup

Change-Id: I35e5c70fff423770a03b5bb39d439ebea82dd56a
Merge remote-tracking branch 'upstream/cm-10.1' into cm-10.1

Conflicts:
	res/values/arrays.xml
	res/values/strings.xml
Merge remote-tracking branch 'upstream/cm-10.1' into cm-10.1
Merge remote-tracking branch 'upstream/cm-10.1' into cm-10.1
Merge remote-tracking branch 'upstream/cm-10.1' into cm-10.1
Merge remote-tracking branch 'upstream/cm-10.1' into cm-10.1
Merge branch 'cm-10.1' of github.com:Team-Hydra/android_packages_apps_Settings into cm-10.1