FastDGGridOperator in driver

See merge request !84

It is not (yet!) suitable for our needs.

This makes the order of 'gradvec' and 'quadvec' consistent with the
other tests.

Note: sumfact_poisson_fastdg_gradvec_nonquadvec does not work!

At the moment loopy tries to acces a vector class variable and throws
a not implemented error. Probably needs some changes in the horizontal
add code.

Introduce explicit FMA node in dune-perftool

See merge request !83

(instead of having the prototype in loopy)

Requires lots of monkey patches...

horizontal_adds in gradvec vectorization

This fixes #57 

See merge request !82

Incude gridfunctionspace.hh instead of utility stuff

See merge request !81

Eliminate trivial reductions

For some reason, the patch refuses to schedule the kernel for sumfact_poisson_dg_symdiff. Mystery bug!

See merge request !79

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

For some reason, the patch refuses to schedule the kernel for sumfact_poisson_dg_symdiff.

Feature/vectorized facet integrals

See merge request !80