CPC: Implement Version 3 Snapshots

[SanPollo]

As the emulator can either load a disk image or a snapshot, this presents a problem if you wan't a snapshot to load directly into a CP/M program, as the disk is not accessible for saving/loading/etc.

Another use case is that you want the user to start on the title screen of a game to save load time, but you still want the disk image available to load subsequent levels.

In order to get around this limitation, please implement version 3 snapshots, which are able to also store the disks in the drives as well as Other Information. e.g.:

More information about the format can be found here.