Consolidate Releasetools/Packaging
* Move /system_app to /vendor (plus put /system/vendor/* in it)
  ~ Less hacky/easier to merge (needs to be in nandroid backups)
  ~ More futureproof (see system/core/rootfs/init.rc note about /vendor)
* Fix {system,userdata}.img partition sizes
* Remove old-style releasetools override and dead code in releasetools.py
* Update updater.sh and remove unnecessary (and backup-breaking) double format.

Change-Id: Id721acd645ddb7ba039d37f99123267a0ea73c1f