Unoriented ellipsoid fit

[ThibaultLejemble]

There exists a method to fit an ellipsoid to points with non-oriented normal vectors (as it is done with a sphere in UnorientedSphereFit).

In the section "3.3. Choice of basis" of the article Non-oriented MLS Gradient Fields, we can choose f1 as scalar field to fit an ellipsoid with constant coefficient c, linear vector coefficient r, and quadratic matrix coefficient L. (UnorientedSphereFit corresponds to choosing f*).

Could be nice to have it in Ponca.