Implement resign in lc0 about lc0

[mooskagh]

Best done via adding bool want_resign; into BestMoveInfo

[gonzalezjo]

Do we want cfg_min_resign_moves to be changeable from the command line? That wasn't the case in lczero, but the naming conventions suggest that it was intended.

[mooskagh]

Why would we ever need to limit minimum number of moves before resign at all... I'd not implement this functionality unless there is justification.

As for resign threshold, that surely should be configurable.

[gonzalezjo]

No idea, but it was in lczero. I'll leave that out, then.

[killerducky]

Just for history: It was originally in LZGo so it doesn't instantly resign handicap games without at least trying. They later modified it with more stuff like scaled based on handicap stones.

[dubslow]

See #47 .

[dubslow]

Closed by #80, I believe.