add support for overriding build.prop settings.

Change-Id: Ie4224d608b7bcb0c2087bd77bc954f8f5f9b6495

Conflicts:

	core/Makefile
include high quality video prebuilts by default

Change-Id: I0d2cb336708e50019ff897089ef78dc5bb7009d0
Signed-off-by: Roman Birg <romanbirg@gmail.com>