Want to finalize a new wings_we:build for colors.

[micheus]

As I had to look into the code to know better about this subject I think the best option (thinking about optimization too) is to use the vc field of #e3d_face{} data structure in the importer.

wings_we:build process that data using the translate_faces before call wings_we_build:we.
Currently, translate_faces is processing only material (mat) and texture (tx) for each vertex of a face. So, there is room to process vertex color (vc) too.

By doing that, it's necessary to create a new wings_we_build:build_half_edges "binding" (?!) and update the other functions called by it.

I believe this is the best and the right way to get the vertex color imported and managed in a native way. That's my thought.