[development] Rating module quality

[Jeff Eaton]

> Off the bat, my first question is whether you're caching 
> totals or not. 
> When 1000 nodes have 1000 reviews each, calculating all 
> totals, averages, etc. on the fly is going to get rather slow.
> 
> --Larry Garfield

That's one of the primary goals of the system -- when external modules
plug in their own calculations (median score, number of votes cast for a
criteria, karma-weighted vote value, whatever) the aggregate data is
stored as a 'voting result' record. Those result records are what get
queried when nodes are viewed, etc.

There's a recalculation hit whenever someone *casts* a vote, but never
when someone *views* voting results.

--Jeff