Consider more cart types

[shish]

Games I personally care about:

• ROM only - Dr Mario, Tetris
• MBC1 - Mario Land
• MBC1 + RAM - Zelda
• MBC3 + RAM - Pokemon

From manual testing:

• ROM-only games work fine
• Mario Land crashes at the end of the first level, if you use the top exit
• Pokemon crashes before the main menu (when it attempts to read savegame RAM?)

MBC1 + RAM looks pretty simple (it's actually what I was aiming for, I'm not sure why mario crashes...) -- I wonder if we can support more types without making the code more complicated (Or maybe it's a good reason to show how each different language handles inheritance / composition?)