Also hide some who-did-this information from normal users

Requires database change
Invalidates caches

Analysis has shown that this system doesn't actually accomplish
anything. Users do not vote on tags often enough to actually get any tag
removed, so why even bother?

Non-critical database change with this commit

This was an automatic mass-replace. Manual replacement of array(...)
will continue

Value added to source field contains the site name and a random string.
This change prevents uploaders from using self-generated torrent files
unless they also add the source value themselves. This value is provided
to them on the upload page, but is still more inconvenient than before.

It's what we were using it for anyway