modular printhead for Ultimaker2 - v2.2

Modular head to aid mounting alternative heads to the Ulitimaker2

Inspired by Foehnsturm (https://www.youmagine.com/designs/ulitimaker-orig-modular-printhead-merlin-ubis) but build from scratch for the Ultimaker2.

I started with a version1 based on a mirrored baseblock of foehnsturm, but due to the asymmetrical rod placement you would lose more buildspace then necessary. I managed the get an almost symmetrical rod placement.

Some remarks;

- you can use this head with the default UM2 firmware, but the margins are small. I only have 1mm of space between the block on the front of the printer when starting a print.

- if you create your own alternative mounts (paste struder, plotter, full metal head,... many projects possible..) you will need to reduce the XY margins in firmware.

- for cable management take 2 tie wraps of the same small size, from 1 you only need the head, mount as in the picture.

- For mounting and un-mounting; remove filament and bowden tube, remove t