Hypercube Tool Changer/Multi Material Parking Extruders

# HyperCube parking extruders

I wanted to experiment with multi material designs for quite a while and after many failures I ended up with this.

I didn't yet quite achieve printing in i.e. multiple colors (I'm working on Slic3r configuration for that) but the main goal is achieved - I wanted to quickly change between an 0.6 and 0.4 nozzle.

I wouldn't say it's my invention as there's a lot of similar things over the Internet and only with the knowledge from there I was able to achieve what I achieved. I designed ass the parts in Onshape from scratch.

With this design you can add as many print heads as your board supports and X extrusion is long :)

At this point there (probably) is no way to control the tool change of this design in the firmware, bellow you'll find Gcode for Slic3r PE (mind that the variable placeholders are different from the original Slic3r). In the firmware you need to have BABYSTEPPING (`M290`) enabled at least on the Z axis to compensate for the hei