fb: less notifications sound (1/2)

add back the 4.3 feature like it was.
User can setup how often notification sound
for an app comes trough so that
it does not annoy to much

Change-Id: I3d7b2ef2e2ff99b7c23880626e0268ec4c5d8543

Conflicts:
	services/core/java/com/android/server/notification/NotificationManagerService.java