Interim quick settings update.

Make existing QS panel available via pulldown from header
(or keyguard status view on keyguard), update the affordances
as a hint.

Don't allow QS to scroll, cap to max rows.

Add scrim over panel to indicate that this is purely temporary.

Bug:14081801
Bug:14059974
Change-Id: I166033975cbc44b91f45ee70ea5c7540390670dd