[NL] Remove IntegrationMethod type from isoparametric FEM class.
md SimpleAssembler. Remove unused id fct arg.
Remove integration method from FemElementPolicy.
Add builder for LocalGWAssemblerData objects.

map from type_index of a mesh element to a 'new' function.
Define DIM and NPOINTS for all ShapeFunctions.
Extend builder to Line and Hex elements.

Adding a template alias to LocalGWAssemblerData<ShapeFunction, ...>.