More configurable gamepack stuff

[Matriks404]

Right now gamepacks supports only bare-bones configuration. It is largely based on how Super Mario Bros. 2 behaves, instead of allowing the game developer more options to do stuff.

• Game type (smb2 (Super Mario Bros. 2), doki (Doki Doki Panic)
• Custom backgrounds for title screen, character select, levelbook and levels
• Animated backgrounds (such as snow or rain falling, this will be useful for Mario Xmas levelpack)
• Custom introductory story line count and width
• Character customization
  • Configurable amount of available characters
  • Walking and running speed
  • Acceleration
  • Speed multiplication when carying block
  • Jump height
  • Strength (the speed at which a character can pick up a heavy item)
  • Configurable attributes
    • Ability to float
  • and more...?