JPN Extruder 2 Gearbox

I added the gearbox for the http://www.thingiverse.com/thing:2195351
The arm could be moved by the servo in to the three position.
On the middle to drive filaments and on the ends to drive the camshafts to select appropriate filaments to feed.

The other possibility could have the fixed gear positions and select the needed driven shaft with the wolf teeth gear locking mechanism.