#718 Backup/Restore users and media

[zdiva]

Add a backup-restore option for users and media.

As it is now, the procedure to backup/restore users and
media does not exist, save of meddling directly with
the database tables. This is tedious at best and
requires an expertise which most phpgedview admins do
not have.

I went through the procedure of transfering to a
different host - so I'm speaking from experience. It
was a HORROR! But, the only other alternative availabe
- to ask all my users (over 100!) to re-register - was
not an option for me, so I went through it, but it
should not have been like that!

I'd say backup/restore users (and media) should be a
paramount feature of any system worth it's salt!