Prusa i2 direct drive extruder for E3D V6 hotend + MK7 drive gear

This is a remix I've made and tested on a Prusa i2. I've done lots of reworks from the original source (http://www.thingiverse.com/thing:887386).

Improvements:
-MK7 drive gear support!
-It is now adapted for Prusa i2 x-carriage
-Remodelled lever. Now uses the standard 623 bearings!
-Pressure system is new making it similar to other Prusa i2
-Hotend now fits perfectly and you're able to install a fan in the hotend without tocuhing x-carriage
-Screw holes have been adjusted and added to f