I wanted to make this a bit more modular, so it's easier in theory to
write external crates that can reuse bits, and selectively compile in
bits, such as adding new systems or new cpu implementations
Also fixed a bug where MOVEA needs to behave differently than MOVE,
such that the data is sign extended to a long and the condition flags
are not changed. I also modifed how Addressable returns data because
I need to return owned data from MC68681, so that the stored data can
be updated (ie. the status flag must be modified after a read)
