vfs_unityed_media: VFS module for sharing AVID projects

vfs_unityed_media: VFS module for sharing AVID projects

Based on <https://code.google.com/p/vfs-unityed-media/>.

The existing VFS module media_harmony has some problems relative to Avid
media sharing:

Avid looks at the modification time of the ingest directory. Since
media_harmony has everyone using the same directory, users (or client
systems) have to somehow create "fake" directories with special names
and then media_harmony returns the mod time of those fake directories
for the different clients rather than the actual mod time of the
communal ingest directory.

To make matters worse, users then have to have a special utility or
understand how to update the modtime on these specially named
directories. Otherwise, their client system will never update the
indexes to show new media.

To make it even worse than that, Avid creates new directories on the
fly, so you can't just set this up statically at the beginning. Avid
will silently create a new directory and your reindexing problems will
start all over until you create new fake directories.

With unityed_media:

* there are no reindexes between clients

* clients don't need to know which directories have been created for
  them, it's automatic.

* clients never have to reindex other systems directories.

* unityed_media let's each client have their own directories.

* unityed_media works much more like Avid's own ISIS servers work.

A module option controls which name is appended to client specific
paths: the username, the hostname (will not work with OS X) or the
client's IP.

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Jan 10 04:15:04 CET 2015 on sn-devel-104