[torqueusers] limit number of job per user

[Garrick Staples]

On Wed, Sep 13, 2006 at 09:29:01AM -0400, Glen Beane alleged:
> There is no per-user equivalent of max_queuable (i.e.
> max_user_queuable), but should be straightforward to add.

That's a good idea.  We should add that.