Description :
This script is used to calculate the center of gravity of a mesh and its inertia elements (its 3x3 inertia matrix)
I wrote it from David Eberly's pseudo-code in his article "Polyhedral Mass Properties (Revisited)" (thanks David!) www.geometrictools.com. The previous version of this script (for Blender v2.49) used a derivative of Brian Mirtich's C code (thanks Brian!).
Compatibility : Tested with Blender 2.80, Python 3 on Windows 7 and Linux Fedora 30.