Property hasInvolvement is required, clean-up around Involvement

[JuergenGrupp]

The class Involvement is referenced from EditorialObject via hasContributor or hasPublisher or hasCreator . While the latter two (hasPublisher, hasCreator) are relicts from the time before Involvement did exist and both pointed to Agent, the first (hasContributor) was introduced, when the class Involvement was still named Role.
Proposed changes:

• For the current modelling, the property that links EditorialObject and ProductionJob to Involvement should be named hasInvolvement according to our naming conventions.

• hasCreator should be kept as property of Annotation , but it should link to Agent , not to Involvement , as it currently does.

• hasPublisher should be removed, as it is fully replaced by an Involvement classified as a publisher.