LED flash when screen ON (frameworks part 1/2)

Add ability to select whether the LED will flash
notifications when screen is ON.

Change-Id: I23e3579847b7c4f3b7f4bca63836ce9d2b5600a8

Conflicts:

	core/java/android/provider/Settings.java
	services/java/com/android/server/NotificationManagerService.java