Added check if edge is at border.
Renamed tree to model conversion module.
Adapted imports to renaming of tree to model conversion module.
Edge comparison and string representation added for model implementation classes.
Simplified string representation methods of mesh implementation classes.
Added vertex indices property for mesh faces.
OBJ file exporter for meshes added.
Basic test for mesh OBJ exporter added.
Model scoring stub added.
Removed redundant faces property on mesh edges.