…rk class

Maybe it will only live here, so currently there is no need for
extraction.

…etName

Offers the same thing but is more flexible (and can be read).

…blems

Remove the challenging problems from the "normal tests" and rather
produce reports showing for which of these problems each minimizer
is failing for specific settings.

…torial

…chmarks

That was simply forgotten.

Let's reimplement useful benchmarks for the "custom problems".