Distribution of players within a batch should be random

[npaton]

Currently within a batch, players are assigned to the games in order until filled (the games' order is randomized before this stage). We want to distribute players coming into a batch randomly. If multiple batches are running at once, fulfill (wait until all games have started, not only fill until capacity, can over-book) the first one started before moving onto the next one.

[npaton]

@amaatouq This should be done. It's complicated, it will need some TLC and as much testing as can be done.