Make feature interactions in plots and textual explanations configurable

[TimKam]

Feature interactions in plots and textual explanations should be configurable, i.e.:

• One should be able to configure to only include feature interactions in a plot or textual explanation.
• One should be able to configure to only include "ordinary features" in a plot or textual explanation.
• By default all ordinary features and all pre-configured feature interactions should be included.

[TimKam]

I think this feature only needs to be documented.