Each template has a datastore, which is really just a subdirectory that can
be populated with files, and committed to the subversion archive.  Note,
the datastore os specific to the template itself. The Template Archive link
on the Show Template page takes you to the subdirectory, which by
convention I am calling "datastore".

The directory actually lives in /proj/pid/exp/eid/TGUID-VERS ... but that
path is printed out for you on the archive page.

Anyway, put stuff in the datastore directory, and then commit the template
archive so there is a tag associated with it.

When an instance is created, a checkout of the datastore is placed in the
experiment directory (/proj/pid/eid/exp/template_datastore). The current
tag (from above) is stored with the instance so that we can later recreate
the enviroment for the instance, say for rerun.

Tarfiles and rpms in the datastore can be referenced as xxx://foo.rpm (in
your NS file).  tarfiles_setup transforms those when the instance is
sw...