- In ProxySOCKS5 don't propose to the server to supply username and
  password if we actually don't have any (we never have). Indeed, the
  server might take us up on that offer, even though they actually
  don't need authentication
- Interactive verification of SSH Host Key when a new account is
  defined. "Add Account" button only becomes active after "Check Host
  Key" has been successfully used.
  If ever ssh server key changes, you need to recheck its key using
  the same button in edit account

