A rico:Activity for authority record creation

[paveljee]

Related issue: #10

Another new entity that is useful for storing some of the info, e.g., the reference to the archivist who created the authority record

[paveljee]

This is currently being discussed, at it is not very clear how creation should be implemented (e.g., CreationRelation vs. Activity). Once we have clarity on this, we can try to implement at the mapping stage.

Also, for lower-level records such as listings, inference reasoning should probably be developed to infer creation info from the parent RecordSet. But, creating explicit triples at mapping is also an option. We’ll be thinking more about that.