3D Part Preview added to Parts Tracker

[Orion Pobursky]

In the latest push to master, I have added support for texmap. By default textures are found in the folder "textures". 

For other placements, the options parameter "idToTextureUrl" can be set. This is a function that takes a texture name and returns the location of the texture file.

You didn’t need to create a new function. The texture path should always be <part path>/texture/<texture name>