V0 Maintenance fixes and Mainsail

 Just had the opportunity, now that the V2.4 is working to undertake some repairs on the V0.

1. Re-built the Z platform. Originally, the screws hold the two cantilevering 100mm extrusions were not tightened and so they were reassembled and also included a L bracket on both the top and bottom for added rigidity. 
2. Rebuilt the X gantry, as I was getting the wobbling idlers at either end, cause the printer to eventually fail. Hopefully, a fresh re-build and re-tighening of the belts resolves this issue. 
3. Changed from OctoPrint to Mainsail. So far, it seems to work well, I like the live Z adjust that was missing out of the box for OctoPrint. 
4. Installed the 0.6mm nozzle for 'fast prints'. Was able to get the Voron cube at 0.3mm layer height 100 mm/sec in around 30 mins, with good quality. This was the first print so needed to re-adjust the extrusion multiplier. I think I need to improve my part cooling to get crisper corners.