2X Extruder Upgrade for Raffle Alu-Cooling Block and Hot End

I have installed Carl/Raffle's Alu-Dual Hot End & Cooling Block Upgrade http://shop.raffle.ch/shop/ and I needed some modifications to get mcniff's extruder upgrade http://www.thingiverse.com/thing:222667 working. What I did:

- Added slight extrusion under stepper gear to help guide filament into the hole and to help prevent flexible filament from feeding/jamming under it (idea from thing 404636).
- made opening for stepper gear slightly larger for better fit with the new guide-extrusion (I