MMU2S - Better Pulley Body

I have made some minor changes. I didn’t have any M5 inserts, so I modified the file to be able to use PC4-M6 Pneumatic Connectors. There were also missing on the file some machinings allowing the passage of the selector screws when it was moved, so I added them.

Thanks to Jfromel for his great work on the MMU2S. And thanks also for sharing;)