This change escapes a parameter in Local_group::setNickname(). Review
of the code paths that call this function sanitize the parameter
higher up the stack, but it's escaped here to prevent mistakes later.
Note that nickname parameters are normally alphanum strings, so
there's not much danger in double-escaping them.
We add a local_group table to store data about local groups. It has
the unique key for nickname, so /group/<nickname> looks up here.
Updated DB data object classes and data files.
