Some changes to add flexibility and remove memory leaks 

When I checked fbx-conv I noticed it was leaking memory. After talking to bach on irc, I tried to add properly freeing memory. Along the way I noticed that the current implementation adds some restrictions and work arounds that aren't necessary. So I decided to take another road:

- Moved everything not needed anymore to the /old folder (can safely be removed)
- Add pretty much the same model structure as the java side, which has mostly the same responsabilities for freeing memory. This also allows to easier reflect changes in the model class on both c++ and java sides.
- Change the loader to be some what more flexible, like:
- Reusing meshes with the same attributes.
- Allow baking uv translate, rotate and scale in mesh
- Add method for listing all textures within a fbx before converting, and add a callback to provide the texture (including translate, rotate and scale info).
- Add links to nodeparts which specify which nodes the blendindices refer to
- Allow to add multiple fbx files to one g3dx file
- Other changes inline with the above

Note that this is quite a change and might require some additional cleanup (like moving code to cpp files :D). I'll review that after this is pulled.