This patch updates the sources-branch-updater convenience script to
make it also check for additional updates relating to policy.json,
paste.ini, rootwrap.conf, rootwrap filters, etc.
This ensures that the SHA updates are more complete and the updates
require less effort to do.
In addition to the script update there are some changes to other
file names and locations in order to facilitate the file's ability
to do everything correctly. The changes enforce a specific convention
for the names and locations of files it manages.
Change-Id: I99899e61e0527639abc8b3bae0296a891607a31d
7ef2a9e48f