SystemUI: Extra Slim Shortcuts && Cleanup

Some cleanup of slim shortcuts
	& implement method to allow
	user to toggle toggleable
	settings to the preferred state.
	Much easier to use with confidence
	knowing you'll be in the correct state.

Change-Id: I897ee4567426d0314952b9860a487ab445795dfc

Conflicts:
	packages/SystemUI/res/values/slim_strings.xml