LockscreenPattern : Toggle dots/error pattern visibility (1/2)

Give user ability to hide error pattern / dots.

Part 2 : http://review.cyanogenmod.org/#/c/33004/

Patchset 2 : Minor formatting
Patchset 3 : Cleanup commit msg

Change-Id: I2af7403b0f72c72e13dd1dec73f8d335ff4029bf