though still mixed up by name with dirichlet bc.

It is badly implemented as is and does not offer value over
writing symbolic functions.

We never really used or trusted it.

Do not annotate FiniteElements anymore, further split driver code

Conflicts:
	python/dune/perftool/pdelab/driver/taskbased.py

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.