Implement some functions in counted Vec4d (pow, select)

See merge request dominic/dune-perftool!228

It does not yet do all the jobs it can do, but it exists and we can
run tests with it.

by introducing an order on the kernel objects and
using the first n kernels instead of an itertools.permutations
generator

We will need even more "levels" in the near future

for further extension

Feature/avx512 vectorization bugfixes

See merge request dominic/dune-perftool!226

So far, it did not set the qp tuple correctly and
thus sometimes resulted in too big numbers being
chosen.

Add sections in generated drivers for much better reading

Closes #109

See merge request dominic/dune-perftool!225