Geeetech i3 X - X carriage set with circular fan duct

An alternative X-carriage for Geeetech Prusa i3 X. Made for a smooth rod separation of 45mm (not the default 70mm). It was designed to have some minor advantages as compared to the stock Geeetech carriage set:

- Easier removal of the extruder from the carriage: Unscrew two M4 screws from the bottom and pull the extruder forward through the gap (backplate.stl)
- Cable gaps for hot-end cables and motor cables at the bottom of the back plate -> No loss of build volume in any direction
- Back-m