Improve Backup System and add UI to Restore Backups

[NinjaPedroX]

NOTE: This PR is based on and depends on the World Manager PR, and will be rebased often to stay update to date with that PR and to get rid of the duplicate commits once the World Manager PR is merged. This PR will be marked as ready for review when that happens, though it may be hard to review this PR until then.

• Made the server back-up the save file every time the server starts up with that selected world
• Added UI and functionality to allow the user to select and restore a backup from within the world settings
• Changed the backups directory to the "Backups" folder within each save file
• Allowed a maximum of only 5 backups
• Changed the server error message for corrupted worlds to tell the user to restore a backup, and it now backs-up the corrupted save files so that devs can troubleshoot

TODO:

• [x] - Add a "backup" command to the server console so that the user can manually back up their save
• [ ] - Fix backup system to be able to deal with save name changes (Changing the name of the world would invalidate the names of the already existing backups)