• new skin for a certain kind of 6-button gamepads
• separate skin list that isn't dependent on the list of currently loaded skins
  Unused skins won't disappear on next load.
• joystick skin now works with non-joystick gamepads
  Unless specified, it's not possible to tell if it's a joystick or not, even if it's physically a joystick. At this point I am thinking of removing 'joystick' mapping property.
• update function to do tasks required to apply changes, to data that can't be altered by just overwriting old files with new ones.