Blockstructured tests may fail, since the interpolation of the exact solution is not suitable

I should work on a specific FiniteElement class or FEM for blockstructuring, s.t. I can remove the element parameter from the blockstructured implementation as well.

Computes tensor index from single index.

This should probably be part of the loopy Mapper but I'm not sure if I could add it there.

This should probably be part of the loopy Mapper but I'm not sure if
I could add it there.

Moves application of transformation from micro to reference element from visitor to PDELab interface

Removes micro_to_macro_index from accum_insn and introduces a class BlockstructuredAccumulationSpace to specialize AccumulationSpace for blockstructured FEM

Merge branch 'master' of ssh://gitlab.dune-project.org:22022/dominic/dune-perftool into feature/blockstructured_poisson

Add readme and script to apply patches

See merge request !157