Fix/svv symmetry

This MR deals with a couple of problems related to the use of SVV in deformed elements. First, in the current formulation the SVV operator is not symmetric in deformed elements, causing problems since this is assumed in other parts of the code. This is fixed by using the local Jacobian to recover symmetry. The second change is that the usual Laplacian operator was taken outside of the filter, to avoid an unnecessary projection of it that was causing simulations with SVV with zero coefficient to give different results than simulations without SVV.