Within our test, we noticed that the value of S was -1e-17 which resulted in weird values. This is fixed by defining sqrtS as 0.0 in case the value of S is lower than 0.0.

Within our test, we noticed that the value of S was -1e-17 which resulted in weird values. This is fixed by defining sqrtS as 0.0 in case the value of S is lower than 0.0.

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

A 3d element that can be used as an interface between a square face and two triangles (nonconforming faces)
Yamakawa hex recombination: fixes + adding trihedra interface elements