MK8 Extruder Mount with built in print cooling ring for Sintron Prusa i3

I had a few issues with the original bracket supplied with the kit. While it worked, it relied on the plastic flexing to get the extruder in and out and I managed to break it. I managed to fix it and it work for a while, but it melted trying to print on a (very) hot day. Some very dodgy fixes made it possible to print an improved version with inbuilt print cooling ring.

This version has a number of improvements over the original:
* Built in print cooling ring and fan
* Make in two parts so