Hypercube E3D Titan carriage

This is a new X carriage for the Hypercube, designed to hold the E3D Titan extruder.

The carriage has been designed with the objective of getting a heavy duty and reliable platform for a continuous production 3D printer. Features are:

* Solid holder for the E3D Titan extruder, direct drive, and room for the hotend fan.
* Uses LM10LUU (long) bearings and 10mm smooth rod for the X axis, for increased stiffness, specially in printers with a long X axis. You can use the default Hypercube XY j