make bacon and custom releasetool (for squished zips)

Change-Id: I4f61b6a6b9b8bab8582fa5423c4134c07af17606
add support for overriding build.prop settings.

Change-Id: Ie4224d608b7bcb0c2087bd77bc954f8f5f9b6495

Conflicts:

	core/Makefile
add support for custom releasetools
build: Fix usage of releasetool
Add otapackage support for backuptool

Change-Id: I512554c579d444067cd3ccbb0e6946a5eb6bc964a