Save two auto saves to minimize corruption

The autosave system now can overwrite data, which when closed without warning can cause corruption. There should be two autosaves, that way if one got corrupted you could load up the other one. There should also be a button to replace the world with the other autosave automatically. This is way better than the current system of clogging memory space with backups, and new players can get used to this faster than backupping. If Mc is forcefully closed, it should encourage you to load the older autosave.