Handling carryovers

I'm not merging this one because I definitely want @puls to review it.
I'm not so sure. How does that allow a Match to count in multiple Phases?

Basically, there needs to be some sense in which Match is many-to-many with Phase. My current thinking is that the way this diff works, in which there is a "main phase" and "other phases", is preferable. I'm definitely open to being convinced otherwise, but so far, I haven't been :-)