Reshuffle FramebufferSurface

FramebufferSurface no longer speaks directly to the FB HAL.  Now
everything goes through HWComposer (which may or may not be
connected to a hardware composer).

Added display index arg to some query methods.

Change-Id: Id3e157d2d4e3555d33afbb703e518b6e92e2d6d5