- added an additional "manufactured" field to the bom view, to distinguish between 3dprinted / bought parts
- still trying to trace the exact origin of issue #62 (stl export): a few things I found
 * it is due to redundant overlapping vertices in objects (that should normally be eliminated by the "canonicalized" method
 * apparently , the canonicalized result is correct but gets broken in the "reTesselated" method that follows

- also started to move a few methods (in CSGFuzzyFactory for now) from map to list comprehension, both for clarity and (potential) speed ups