Lockscreen: Add checkbox for quick unlock

This is the Settings part needed for:
  http://review.cyanogenmod.org/#/c/54898/

Change-Id: Ibd12681a972806da4bd6f87c341ddd404dbabdd1

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