User Registration Update

I've added a spam filter to the user registration form.  I'm going to leave it be for a few days to see how well it works.  If it blocks most of the fake registrations (which have accelerated to ~50/day) then I'll disable the requirement that accounts be approved by an administrator.

If it fails, then I may have to rely on CAPTCHAs.  And I really don't want to do that.  I've always found them annoying.