Better color support

[assertivist]

Vertex colors are somewhat difficult to use in Blender. On top of that, it has no awareness of what the Marker colors are. The exporter should allow you some options like

• Use only the marker/marker2 color for all faces
• Change color X to the marker color
• Use vertex colors set on the model

Currently the exporter only does the latter and offers no options to the user when they hit export.

[assertivist]

Vertex color import/export has been updated to the new indexed format. The code is there to handle marker colors, but currently the plugin just gives the value of the marker color. This can be extended to do something different though.

Also, alpha is not handled right now, but not because of Blender, but because of the color parser I picked.

I'm afraid of adding non-pure-python requirements to the blender plugin because I imagine installing libraries into Blender's copy of python is not very straightforward.