This adds support for "templates" source.properties files that can
inherit the platform version/codename/api level from the build.
The purpose is for a given build to always generate SDK files that
match the platform generated in the same branch.
Change-Id: Id623bbef45a04d953da8eade7e8c34c77709f9c3
Also fix packaging of system image (it had an extra root
directory in it, e.g. it was packaging android-4/armeabi-v7a/
instead of just armeabu-v7a/)
Change-Id: I0254b2680168d25103222f8871b2af37a7406b58