Lockscreen: Add checkbox for quick unlock

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

Change-Id: Ibd12681a972806da4bd6f87c341ddd404dbabdd1
Merge branch 'cm-11.0' of git://github.com/CyanogenMod/android_packages_apps_Settings into cm-11.0