Support multibank ROMs for Distella files

[thrust26]

Currently DiStella only creates correct files for non-bankswitched ROMs.

[sa666666]

This shouldn't be too bad for the standard schemes: F8, F6, F4, etc (and SC versions). The more esoteric ones will be more challenging, of course.

The main pros are:

• the debugger/bankswitch class already has all the information we would need, and the classes are already abstracted though inheritance
• it can be done one scheme at a time, and added to each specific class individually