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.

It is not necessary anymore

It is applied to the function call...

Omit cmake generated main function

Closes #118

See merge request dominic/dune-perftool!235

As a step towards making the driver the main function.

Implement possibility of functions that provide their own visitor

See merge request dominic/dune-perftool!234