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.
