Add matrix of inertia

[kmarchais]

This pull request introduces the implementation of the inertia matrix.
As indicated in issue #1453, this functionality is already accessible in OCP.

• The implementation returns the inertia matrix in the form of a List[List[float]].
• Additionally, a corresponding test has been developed by calculating the inertia matrix for a cylinder and validating it against the theoretical value.

This is my first PR here, I will be happy to have any suggestion to improve the code changes.
Apparently the tests are failing (even on master for me) on tests/test_cadquery.py::TestCadQuery::testSweep.

[adam-urbanczyk]

Could you run black form this repo https://github.com/CadQuery/black (or 19.10b0) on your changes?

[kmarchais]

Sorry about the different formatting style, it should be better now

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (79e64e5) 94.35% compared to head (8ee2e58) 94.42%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1460      +/-   ##
==========================================
+ Coverage   94.35%   94.42%   +0.07%     
==========================================
  Files          28       28              
  Lines        5809     5778      -31     
  Branches      993      983      -10     
==========================================
- Hits         5481     5456      -25     
+ Misses        197      194       -3     
+ Partials      131      128       -3     

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[kmarchais]

The test has been updated.

The implementation of matrixOfInertia has been inspired by the centerOfMass and computeMass methods, which, if I am not mistaken, have not been tested. Should this pull request include tests for these methods as well?

[jmwright]

Thanks @kmarchais