Fix Issue #92: coeffs. of the polynomial reg. are now public
- The coefficients of the (ordinary) polynomial regression are now a read-only public property.
- The coefficients correspond to the coefficients of the origin polynomial. Specifically, in the case of Lagrange polynomial as the origin, the coefficients differ from the coefficients of the evaluation polynomial (Newton).
- The test suite has been extended to cover the new property.
This MR should resolve Issue #92 (closed).