Add utilities CoarseGridViewFunction, FineGridViewFunction and GeometryInAncestor

This adds three utility classes to adapt grid functions defined on some entity set to a gridView within the same set.

• FineGridViewFunction(f, gridView) represents f as GridViewFunction on the gridView if the entity set of f is finer than the grid view.
• CoarseGridViewFunction(f, gridView) represents f as GridViewFunction on the gridView if the entity set of f is coarser than the grid view.
• GeometryInAncestor works analogously to geometryInFather (with a very reduced interface) but across multiple levels and is used to implement CoarseGridViewFunction.

Here we used the natural definitions:

• A is finer than B if any element e in A has an ancestor element (maybe identical to e) in B
• A is coarser than B if B is finer than A.