#23 Heuristics checkpoint

Getting expected results in...

- Checkers (wp+wk vs bp+bk, nothing for blank)
- Breakthrough (white vs black)
- C4 (disabled)
- Pentago (disabled)

Wouldn't expect piece heuristic to be valuable in C4 or Pentago because there's no way of taking a piece and/or placing more than one piece per turn.