Kill mutations in binary for visitor

Mutant will need subject specific configuration in future. This symlink
trick to avoid spec duplication is not really future proof.
Add full mutation coverage

All mutations occure in shared code of baseclasses. There is no value
to add dynamic class_under_test subclasses over and over again to kill
these. I decided the subclass specs must kill the private base class
mutations. Mutant needs to be configurable here soon.

The subclass specs are run on base class via symlinks. This is not the
ideal longterm solution.