Now other repositories can configure special remotes, and when their
configuration has propigated out, they'll appear in the webapp's list of
repositories, with a link to enable them.
Added support for enabling rsync special remotes, and directory special
remotes that are on removable drives. However, encrypted directory special
remotes are not supported yet. The removable drive configuator doesn't
support them yet anyway.
Actually 3 forms in one, this handles the initial passphrase entry, and the
confirmation, and also varys wording if the same user or a different user
is confirming.
