Reverse engineer level data

[Calinou]

Related to #1.

To play the game, we need to figure out how to load levels and their textures from the original MDK data files. From what I've seen, levels are loaded using some kind of chunk system, but we can probably load everything at once on today's hardware (at least as an initial implementation).

I don't know how gameplay triggers were stored (in the level files or in the executable). Gameplay triggers will need to be ported somehow, likely by creating Area nodes at run-time that are connected to functions implemented in GDScript.

Gameplay triggers are quite varied, and many of them are only used in a single level. Some examples:

• Display a message at the center to the screen.
• Open/close a door.
• Start a different music track.
• End the level.
  • In some levels, this happens after a boss was killed instead.