Revision of printed information for methods in `data_structures.py`

In GitLab by @hehnen1 on Nov 1, 2017, 09:46

The provided information by the objects defined in`data_structures.py`, when requested via `print()`, needs to be revised. Some of the objects provide less information then they actually contain, e.g. `Parameter`. This makes tracking of errors for improperly set up input files difficult.