Make anisotropic quadrature order possible for non DG examples.

It was the wrong level of asbtraction!

But only when they are actually used!

That was a bad idea from the beginning! It lead to a situation,
where calls from within a generator inherited their context tags.
Should be fixed now.

Conflicts:
	python/dune/perftool/pdelab/quadrature.py

Stage instructions are not the solution.