Incorporate Pure/Partial/Full Explanation

[mmschlk]

For ease of use we should incorporate the distinction between pure/partial/full explanations as described in this paper and this repository. This might need some adjustments in "what can be explained" in the Explainer classes as well as additional game-theory functionality.

This distinction should be included in:

• Explainers
• Exact Computer
• as standalone functions (which probably are the backbone for the above usages)