referee

I'm trying to put together a website for our local AYSO region to manage team, field, and division organization. ULT is awesome so far for all of that. One important piece of the puzzle is referee assignment, which does not appear to be a function of ULT.

Here's what I am trying to do for referee assignment:
- User accounts may be added to "referee" group (already got this)
- User profiles may specify referee certification level/age group (already got this)