Simple library to make working with STL files
(and 3D objects in general) fast and easy.

Due to all operations heavily relying on numpy this is one of the fastest
STL editing libraries for Python available.

Prerequisite for Cura update submitted by greg@unrelenting.technology
With some changes. Rest of updates will come in separate commits.

PR: ports/249468
Submitted by: greg@unrelenting.technology