Autogenerate collision meshes

[LocalInsomniac]

Implement a way to automatically generate collision meshes for models in-game. The workflow is as follows:

• If a model or any of its submodels have collisions enabled, the game will look for its .col files and, if not found, will generate them with a warning in the console.
• When generating collision meshes, look in each mod for surfaces.json to identify materials and autoassign the specified surfaces and collision flags for each triangle. Any material not specified in the file will have no collision.
• Typing colexp into the console will export all generated collision meshes as .col files.

[LocalInsomniac]

Won't be done for a looong time, use PNMC in the meantime,