[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/

patchset 3:
    shrink a couple of long lines
    remove power_notifications_use_default option (folded into ringtone option)
    load default settings in global instead of system

Change-Id: I36a6b9f924d2cd52191a8e83a744745b37c5b068

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