Adjust crazyhouse increment schedule

[isaacl]

Feedback for 4+1 was largely positive. However some pointed out that 4+1
is a shorter time control than 5+0 and crazyhouse doesn't have any 10+0
tourneys like standard chess. So bring back a slow tourney, the +2 gives
a very different feel for zh where games last until they are done.

Also add 3+1, which has been suggested a couple times. The logic is setup
to avoid 2 consecutive increment tourneys.