Import polygon parts generated for the 2D nesting core in Mobius

This issue is related to #349 (closed). As Mobius comes with its own representation of polygonal parts, these parts are foreigners in Analysis Situs. Practically, this means that we cannot try out different OpenCascade functions on them, e.g., planar offsets. For the sake of prototyping, it will be convenient to have the possibility of loading these parts into Analysis Situs.

Highlights:

• Let's add the misc-load-polygon-part command. As the polygons come in named, we do not have to specify the name as the input argument.
• The loaded polygon can be turned into a TopoDS_Face with polygonal wires.