Investigate Local2Global function

While implementing #1624 (closed), it appears a loop there is highly doubtful and might in fact work only in P1 geometry.

for (unsigned int i = 0u; i < Ncoords; ++i)
{
....
   const double shape_fct = geometric_elt.ShapeFunction(i, local_coords); // i is a LocalNodeNS::index_type...
....
}