* refactor some code.
* Generate moves instead of states for every possible move.
* keep cloning for the moment.
* Change the key for PieceList.
* Small optimisation for children states generation.
+ Add default value for hashMap (EmptyPiece).
+ Add toString method for Move.
! fix UserMove piecelist bug.
* use piece list for bishop. !!!!! Fix getK method for pieces.
* use pieceList for generating moves for other kind of pieces.
Merge commit 'de1cad6047d20dd383d03d308f40b23c0bf70bc5'