Fan for CatNozzle

Preliminary version, a fan for CatNozzle, an allmetal hotend from Catalonia (Spain). It could be modded to any other hotend. Last updates and scad file here: https://github.com/ChemaFuji/CatPrinter/blob/master/extra/catnozzle_fan.scad
The original is 40mm fan. Added a 50mm fan version.