Implement dataclass decorator?

[jlandmann]

Just another suggestion: It's a Python 3.7 feature, but might be handy e.g. for the MassBalance class
See PEP 557

[yweidmann]

Good point. As soon as we migrate to Python 3.7 we should add the dataclass decorator to all classes of the package DataObjects (except of the Enumerations and Exceptions).