Added Saving/Loading.

Because of my GDScript coding style preference I had to do a lot more work on this than one would probably expect.

Added:

• Saving/loading
• Button that instantly deletes your save

Fixed:

• Maps could be unlocked “more than once”.
  • In quotes because it had no visible effect on the end user unless one played it enough times to overflow the array. Probably around nine quintillion times. I don’t recommend trying though.