Handle annotations on punned types when rendering RDF (issue #183)

Previous code had special case for class and individual;  if used with an anonymous individual as annotation value, a new annotation would be generated for every punned type and annotation, every time a file was loaded.

Turtle renderer has no easy options for forcing node ID, so problem is fixed in Renderer Base.

The fix iterates over all entities of each type, building a map with the counts of the number of entities named by the IRI.   This imposes an extra time and space  cost linear in the number of entities.
Undeclared entities are not considered to be punned. Changing this could remove a test from renderUntypedIRIAnnotationAssertions()