Plan for save states

We need support for emulator-style save state files that preserve *ALL* running game state

This is most needed for the android port, so it will be possible to auto-save everything about a running game when you background it. Returning to the app later provides no guarantee that it will still be running, and often results in restarting the app.

This could also be used on other platforms for emulator-style save states, if the game author wanted to leave them enabled.

I think it would be easiest to treat save states as a separate format from RSAV saves, rather than an extension to them. Or perhaps save states should be a superset of RSAV, where an RSAV format save is embeded into a larger save state reload document