move responsibility for parameterset extraction into parameterset class

[RonnyPfannschmidt]

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[coveralls]

Coverage increased (+0.004%) to 92.683% when pulling 4a436f2 on RonnyPfannschmidt:extract-extract-parameterset into def471b on pytest-dev:features.

[coveralls]

Coverage increased (+0.004%) to 92.683% when pulling 4a436f2 on RonnyPfannschmidt:extract-extract-parameterset into def471b on pytest-dev:features.

[nicoddemus]

Nice refactoring 👍