for further extension

Instationary stuff not fixed so far.

We mistook a tag for an Id here...

We havent got a nonlinear sumfact test case so far, so this one did not break.
test coming soon.

By using loopys group mechanism. Each sum factorization kernel
defines a group that conflicts with all other sum factorization
groups.

Conflicts:
	python/dune/perftool/sumfact/realization.py
	python/dune/perftool/sumfact/vectorization.py

Save all stage 1 sum factorization kernels that are used in
accumulation expression in the cache during the dry run. Discard all
inactive sum factorization kernels in decide_vetorization_strategy.

We recently learned that usage of sub_elements in UFL is ambiguous...

The y ar enot properly implemented right now, do not seem
to be necessary and conflict with recent changes in loopy.

Avoid having kernels interleaved.

Some kernels were not properly instrumented before