Ultimaker 3 (& 2+) filament drive

I take no credit whatsoever for these designs, they belong to Ultimaker. I just went ahead and converted pretty much all the needed files from their GitHub to STL (except for the bearings, springs, etc of course). I noticed none of my CAD programs except FreeCAD could open the step files, so I made it a little easier by already uploading the converted STLs. Also, an assembly to print the right filament drive is included. I did not include the Flow Sensor Cable Clip since development was disconti