Implement user profile backups

[aggregate1166877]

Details:
User profile backups were initially meant to be implemented in #48, however profile backups are not really essential so early in pre-alpha and time constraints for the task were exceed. This ticket should continue that work.

Original task:
Create backups of the profile before it's written. If writing the backup fails, abort. This allows us to 1) restore to a working save on catastrophic failure and 2) means we can pre-emptively check for write issues that might corrupt the profile in use.

It should be noted that this task will only be consider low priority as long as the game isn't yet a proper (fun/playable) game. The moment we have real players doing real things, this task becomes top priority if not yet implemented.