Quicksettings: Immersive: Make last active state a system variable.

Will persist after reboot.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Change-Id: I8f9f62d67e7de079e59ce5292604efacec042bcf

Conflicts:
	core/java/android/provider/Settings.java

Conflicts:
	core/java/android/provider/Settings.java

Conflicts:
	core/java/android/provider/Settings.java