Improved Cyclone Separator

The [original Cyclone design of Boopidoo](https://www.thingiverse.com/thing:3841788) is already good.
But the connector for the tube was rather small, so I redesigned it for tubes with 25 mm outer diameter. (This is **customizable via OpenScad**, just alter the *modification.scad)

Moreover, I made the fan more aerodynamic.

Note: as the openscad files base on the original stl files, these are included, too.