Hygiene: Kill closeOnBack property and OverlayManager FIXMEs

All overlays now use the overlay manager and all future overlays
should also use the overlay manager

Thus all overlays should close on back.

Move methods needed by search from Overlay to SearchOverlay and attempt
to kill them in a future patch

Update out of date FIXMEs.

Change-Id: Ifb048a60106cf141d91c4ca1478a8e0c4efa7836