updates VTKSequenceWriter explicitly

See merge request dominic/dune-perftool!221

Update submodules

See merge request dominic/dune-perftool!238

Feature/transformation based instrumentation

Closes #120

See merge request dominic/dune-perftool!237

Implement sumfact kernels in separate functions

Closes #75

See merge request dominic/dune-perftool!236

fixes the deprication warning for the blockstructured fem introduced in PDELab 2.6

See merge request dominic/dune-perftool!239

Avoid explicit doubles.

The check fails in recent CI, but I think it should be correct
anyway. Also, I dont think that error bounds below single precision
accuracy are good for numdiffs.

No substantial changes there.

They are not used in a senseful way anyway and loopy
stumbled over them.

This is currently only used for level 4 instrumentation,
as these start and stop markers were messing heavily with
dependencies in the sum factorization code. This way, the necessary but
ugly work of adding instrumentation is separated much more
nicely.

I was tired of the amount of ifs that changed behaviour
depending on stage 1 or 3. This is a cleaner approach.

This is a temporary fix for CI. After updating to
loopy 2018.1, this should be properly fixed.