#1586 Implement SecondPiolaKirchhoff operator in local coordinates.
This is the first step towards shell elements implementation. The idea here is that we will define everything in the local basis and introduce the metric tensor. The formulation becomes a bit more challenging but all in all we should get the exact same result as for the cartesian case (which is the one currently implemented). We can even hope to see some performance improvements as there are less operations required.