SmartrapCore 1.0 modified Simplex extruder (for Nema 17 & Bowden) V. 0.5

I made my own adaptation of the Simplex extruder (http://www.thingiverse.com/thing:91054) which is used by default on the prototype of the SmartrapCore printer with a Bowden and a Nema17 stepper motor.

It's actually small changes, but I needed these :
- smaller size (no need to waste PLA, right ?)
- as the insertion hole for the filament is underneath for the Bowden version, I made this hole easier to find (prominent border, and conic shape to make it easier to introduce filament)
- nut