Wrench Holder (parameterized, modified)

This is a modification of the wrench holder by dede67, modifications include:
- defaults to my wrenches with sizes of 7-19mm (they're a bit all over the place since all of my wrenches are not from the same set originally)
- uses M6x60 bolts and nuts for assembly of the holder instead of M4 bolts and a threadcutter
- a better (or atleast different) wrench grip shape
- reduced repeating of the same values in the openscad file and made it slightly more understandable -- sorry that it is still mostly in german.

The picture of my print in orange ABS on a modified Anet A8.