fixes a nasty bug, where face information was omitted

By implementing repr such that instance addresses are
not part of sorting anymore

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