Improved probing the remote server, so it gathers a list of the
capabilities it has. From that list, we can determine which types
of remotes are supported, and display an appropriate UI.
The new buttons for making gcrypt repos don't work yet, but the old buttons
for unencrypted git repo and encrypted rsync repo have been adapted to the
new data types and are working.
This commit was sponsored by David Schmitt.
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.