#139 Allow saving in Action Replay format

[Suggs bill]

It would be a nifty feature if a game could be saved in
the format that the action replay uses. This way saved
games could then be uploaded to the action replay for
use on a real GBA. It would also be nice to be able to
import the save file the Action Replay creates as well.

This wouldn't encourage piracy as the saved game is not
a complete rom image, its just the "battery backup" data.

I don't know if anyone has details on the save format
the Action Replay uses though :/