Heads up: option to disable in lockscreen (1/2)(RB)

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/BaseStatusBar.java

Change-Id: Ib002ebf52ee834968765f9a00356ee45a85adc1e (reverted from commit fa9527efd201ed75140453eafc6a5aed78a47c43)