Enable unlimbited gauntlet with Cello bow holding attachment

This was designed with the help of Team Unlimbited (http://www.teamunlimbited.org), and can be printed and assembled by following their instructions. A video of it in use can be found here: https://youtu.be/LmcIhVnmvjw

The big difference is the hand, which has no fingers. The hinge can be completed with a piece of filament as the pin, just use something hot to make the ends slightly bulbous so it doesn't fall out. Better to use 3mm for the hinge pin, 1.75 will be a bit loose (but also works i