Corrected 3D geometry: issues with the use of Boundary and CombinedBoundary and the removal of some surfaces of the boundaries of the (conducting) cores. Function Abs() has been added.
New 3D geometry generated with opencascade tools.
Adding the possibility of weakly imposing div j=0 for the source. It seems to be necessary with the tree-cotree gauging and the old geometry. The new geometry and mesh does not seem to be so 'touchy'.