Also fix return code in WHIP.

The group and name are in the path, this avoids redundancies.

It was only being enforced in the client.

Rename the fallback-users entry to wildcard-user, and only
allow a single fallback user.  This is missing the HTTP API.

Suggested by Dianne Skoll.

This avoids displaying "internal server error" when a username
is disabled.

Double-click, because otherwise it interferes with selection.

Otherwise warning messages during upgrading cannot print the
filename.