whoops
less std::function, more speed
generate moves that leave our king in check, in which case generate for the opponent only a king-capturing move.  about a 50-fold speed increase (measured by mcts)
test new king capture handling
let make_move_on_* and update_* act on member variables
update winner determination
these are long gone
fix bug in winrate computation
mcts statistics, and a performance test for convenience
use doubles for playout result so we can have draws be 1/2 without complications like result_factor; also backpropagating 1*result_factor - result inexplicably resulted in computation getting slower with each additional sample, whereas backpropagating 1 - result (which was a bug) resulted in constant time per sample. crazy\!
disable speed test for now