Replace stlwriter.py with python library

Maybe trimesh : https://github.com/mikedh/trimesh

Allows textures / transparency for eventual Device inclusion in outputs

added enhancementusability cleanup labels

changed milestone to %0.4.x

marked this issue as related to #23 (closed)

we already use numpy-stl in display3D so we can just send around meshes

mentioned in merge request !19 (merged)

closed