Draft A Sensible Bit Arrangement For Move Flags

[Willilio]

This is something that will require some thought, but needs to be thought about considerably. Firstly, does the move flags field need to be a U64 (8 bytes) to hold all the information. Will an 8-byte data type keep the struct optimized or is there some way to hack the system so that a smaller data type can be used. Also, I need to decide what kind of bit arrangement is most sensible and which pieces of information are worth storing in the flags. Promotions and en passant are obviously important, but what else (maybe check? checkmate? capturing?)