Test En Passant Moves in Bitboard Move Generation

[mx-e]

• We should be able to check wether en passant move are correctly detected, when a en passant field is set and the situation allows the move
• We should be able to check wether en passant field are set correctly when executing a pawn double move
• We should be able to check if en passant fields are set and unset correctly when pushing and popping moves from the move stack