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

This reverts commit ab3d364dda0ec6fca6557f7927d028be3818de92.
Heads up: option to disable in lockscreen (1/2)

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

Change-Id: Ib002ebf52ee834968765f9a00356ee45a85adc1e (reverted from commit ab3d364dda0ec6fca6557f7927d028be3818de92)