build: Add support for vendor product and device name

 * CM's build system assumes some convention-over-configuration which
   we might need to override in order to conform to vendor requirements.
 * Allow overriding of target and product names using these new
   variables. This allows for CM conventions to work, while generating
   the correct fingerprint dynamically without post processing the
   strings.

Change-Id: I7e095bc2e185bef815ec4f5869ec4df85c47e96a
add support for overriding build.prop settings.

Change-Id: I59503da73cf64f48b45401320d162ac1dad2d2c0