Add back notification light settings.

Change-Id: I474a14a1b395407f5ca273a5d6a3a7f03f7e4698
(cherry picked from commit 0c8eceaf1d0b4af5e16d7b683e113485570093f5)

Conflicts:
	AndroidManifest.xml
	res/values/cm_arrays.xml
	res/values/cm_strings.xml
	res/xml/display_settings.xml
	src/com/android/settings/DisplaySettings.java
	src/com/android/settings/Settings.java