Async Model Loading

[mcmonkey4eva]

Renderable models should load asynchronously.
Collision / internal model data should be able to load asynchronously.

Probably this would function as an "empty" VBO / collision mesh, that can be used fine, but is later substituted in with the real model once loaded.

This would function with callbacks and such.

Server data should just refuse to handle a model until it's loaded (EG spawn a plane, plane just isn't there until the plane's model is loaded...)

[mcmonkey4eva]

Same for textures too probably. Defaults to a white texture probably.

[mcmonkey4eva]

Basic texture/rendering-model loading is now async.
Collision loaded is semi-async on the client, still needs to be async'd on the server.
There are still a few cases to account for as well.