FABtotum Protohead v6 Bowden

EDIT: Two additional ducts just added. Improved_duct_4 works reasonably well at 0.15 mm layer height and is well-tested. Improved_duct_5 is just created to distribute cooling along two axes (the directed perforations towards the nozzle are inspired by the digital solar clock, http://www.thingiverse.com/thing:1068443)

All the FreeCAD source and further information is here:
https://github.com/imarin2/ProtoHead_v6

The original Protohead v4 is here:
https://github.com/imarin2/ProtoHead_v4