Major turtle changes: We now have turtle for: (1) contributors for images, figures, chapters, and reports, (2) turtle formalizing the person-organization-publication relationship, and (3) turtle formalizing the image-dataset-activity relationship.  Additionally, (4) modified turtle to reflect report relationships/prov of "citedBy" and "cites"

Minor change to turtle for contributors, and added code for "contributors" for person (see d-s/person/...)
Subject to change depending on feedback.