Automatically create backups of saves when they are opened

[budak7273]

Perhaps make a subfolder in the saves folder and copy the save there with .BAK or similar appended to the file extension.

[Goz3rr]

Yeah we should definitely do this, although we could probably do it on save instead of open. How do we want to handle duplicate backups?

[budak7273]

Perhaps append the date and time to the save file? Maybe .BAK#? Regardless, we should probably limit it to only a few backups per save.

The save files compress exceedingly well, so we may want to consider zipping the backups as well.

[budak7273]

Closed by #111