Add StudentObjectiveAssessment to UML to clarify how scores and performance levels are modeled for sub-elements of the student results

Since these don't show in the UML clearly, it is not obvious where to place scores and performance levels.

This should be shown as a callout or in another manner to make clear that these are not domain entities / core elements of the model. 

This will involve creating a new documentation convention for showing elements inside an entity.