Non-fastdg: Permutation of the input happens before the sum factorization
kernel when we setup the input. This is done by a method of the corresponding
interface class.

Fastdg: In this case the input will always be ordered according to x,y,... This
means the permutation needs to happen in the sumfact kernel. Since we want to
vectorize sumfact kernels with different input permutation in an upper/lower
way we need to do this permutation in the corresponding interface class. This
is done in the realize_direct method and in the vectorized case the
corresponding methods of the scalar sumfact kernels are called.

So far only for fastdg. This should also happen in the non-fastdg case.

Note: They are not yet used but in the long term the permutation should be
handled here since it is about input/output setup.

Note:

- direct_is_possible true/false could probably be handled in an upper/lower
  vectorization way.

- Vectorization of SF kernels should be based on cost permuted matrix sequence.