Multi-Extrusion system for Scalar 3D Printer

# Description
These parts are used to make Scalar 3D printers compatible with DUal extrusion.

Dual extrusion is made using a "Y" like convector.
This system is based on the idea from "distechautomation" who is making the Prometheus Hotend providing a dual extrusion system using 1 single hotend.
The idea was then taken back by Prusa Research and improved to 4 color system using a multiplexer board. The multiplexer board makes it possible to use this system with 4 extruders using a standard Ramps 1.4 board and a single stepper motor driver!

We redesigned the system for a simple 2 extruders system so that it can fit our Scalar 3D printers.

# Compatibility
These parts are compatible with 1.75mm filament only for now.
It was tested using E3D Lite hotend.

# What you need
- 2 Pneufit connectors ( http://3dmodularsystems.com/en/mechanical/223-m6-push-to-fit-pneufit-connector-for-4mm-od-ptfe-tubes-compatible-with-175mm-filament.html )
- 2 PTFE tubes for 1.75mm filament (lengt