This reverts commit 211fa521, reversing
changes made to 8ba56d73.

- uniformize names of new api functions
- remove unnecessary args (dim, nbrIntegrationPoints, ...)
- cleanup ElementType::functions

Bézier coefficients computed for the product of two or three functions are now ordered as the original convention (corner coefficients are the first)

Add a validation code in MetricBasis to check that the process: "computation of Bézier coeff, subdivision and interpolation" is correct for Metric (thus also for Jacobian in 3D).