More work on FreeCAD

These days I had less time to work on FreeCAD, but I've been working a bit to solidify the Arch module, and refined a bit the 2D export. There are now 2 modes, solid, which uses the Arch vector renderer, and wireframe, which uses the standard Drawing module algorithms. That last mode now also draws sections with thicker lines (settable in the Arch preferences), and can also show the hidden part, behind the cutting plane.