openscad: metric nutsnbolts library

This is a library that allows for easy creation of screw throughholes, screws and easy documentation of materials.
It allows to directly use the _name_ of the screw/nut size you want to work with. No more looking up screw sizes, while clearances can still be set via parameters. Look in the code, there is extensive documentation on the available parameters.

Btw: Visit my github project for the latest version: https://github.com/JohK/nutsnbolts

If you are more interested in printing