Settings: Add support for variable size pattern lockscreen (Part 2/2)

Part 1: http://review.cyanogenmod.org/#/c/28533/

Forward port of: http://review.cyanogenmod.org/#/c/20614/

Add a menu to choose the pattern unlock screen size (currently 3x3 to 6x6)
Default size is specified in the frameworks

Patch Set 1+2: Initial port

Patch Set 3: Use AOSP code style

Patch Set 4: Fix copy/paste issue

Patch Set 5+6: Comply with framework changes

Change-Id: I5e3d1f8b19b7f5017c854ab9d28b459214f00949