[1/2] Forward port power connect/disconnect notification support

Original commit info:

    [1/2] Power connect/disconnect notification support

    part 1/2: frameworks/base PowerUI and Settings
    http://review.cyanogenmod.org/#/c/35241/

    part 2/2: packages/apps/Settings Sound settings
    http://review.cyanogenmod.org/#/c/35242/

    Change-Id: I36a6b9f924d2cd52191a8e83a744745b37c5b068

Change-Id: Ib865e1c296cb8e1d957b2a48616c88ceaba5c008

Conflicts:
	packages/SystemUI/src/com/android/systemui/power/PowerUI.java