#29 Set minimum weight for mobility heuristic
Merged 'develop'.
#29 Make HeuristicScoreInfo an inner of PieceHeuristic
#29 Very minor code tidy during code read
#29 Partial implementation of getHeuristicValue for mobility heuristic
#29 Fine to use the same underlying state machine throughout the heuristic

Because heuristics are always called from the single tree thread, not the workers.
Use half the available processors
#29 Get initial mobility state
Merged 'develop'.
#29 Basic mobility-heuristic

- Basically works
- Not well tested
- Only 1 heuristic can work just now, so disabled in favour of PieceHeuristic
#29 Spend half the meta-gaming time on heuristic weighting