Kh2 MDLX export to FBX and Assimp utils

[osdanova]

Export functionality to FBX for the MDLX editor. It uses Assimp, so it should work with other file formats, I've only tested with DAE and it requires correct offset matrices (I think), which I'm not calculating right so that's broken right now. Added Assimp utils library to make use of Assimp easier and have a basis on how to parse models with Assimp.