Handle multi-game matches

[bsmithgall]

This will require some reworking of the internals, but it would be nice to support multi-game matches per round. Right now, the assumption is that you have a single "game" per round (which has a unique link, winner and loser, etc), but it would be cool to support something like "first to 2.5" style scoring.

Probably the way to do this that is lowest lift to what exists now is to do Tournament -- 1:M --> Round -- 1:M --> Match -- 1:M --> Game.

Then the Tournament could start taking in some configuration options. This would also be a nice way to jumpstart into support for a round-robin style tournament (everyone plays everyone else).