Add support for Bernstein interpolation

It could be interesting to add support for bernstein polynomials. In general, they should give the exactly same result as Higher order lagrange interpolations, but they differ from lagrange interpolations in that they are not interplatory at the interior nodes. This breaks some assumptions in the code, for example when adding non-homogenous dirichlet conditions, or in the `apply_analytical!` functions (and maybe more).

So they could be added as a nice way to check for correctness :)

Fourth order bernstein bases: