Revert "do not reduce the counter move"

This reverts commit a3d5e62d39651c11239a56c89cc4864c738b3a91.
Revert "counter move heuristic"

This reverts commit 76d95141c5b3416f09fa836d48bcd2bbab8cbe76.
make board return a double move key
struct Refutation
plug double move refutation hash table to search and move sort

2812-2747-4441 [50.3%] p-value=80.8%

signature = 8668789
try to get a proper double move at ply <= 1
Signature unchanged, as change is context sensitive (position fen and position startpos moves ... would give diff results)
signature = 8668789
Revert "try to get a proper double move at ply <= 1"

This reverts commit 476aba41a08d4d84d47694849ba34359ee932d17.