comment out the behaviour that tries to aggressively reach 2048 at the expense of longer-term benefits
AI fixes
- fix minmax algorithm, we want to minimize the score during a computer move
- add the ability to switch off adversarial mode; in a naive run it's easier to see if fitness function works
- use the same scoring method in both player and computer phases
optimise grid metrics functions so AI tree search runs more deeply in the same amount of time