Improved build system for the boot ROMs.
Better comments in the ROM code.

Allows usage of pytest for testing python code.

CGB is now going to boot using Boytacean ROM by default.
Allows better image and open source only boot.

Making it possible to indirectly access the registers via constants.

Adds OBP0_ADDR and OBP1_ADDR to the list of registers.

Without flush we would might be loosing some bytes in writing.
This is explicitly stated in https://doc.rust-lang.org/std/fs/struct.File.html.

Also adds more explicit error handling in state related code.

Also adds flush operation after writing to file.

There's a new rust stable version.

Allows better understanding of the message.

More standard support for the `BusComponent` interface.

Allows blargg's test ROM to pass.