Take advantage of the Model inheritance provided by polymodel.PolyModel to
have create a class hierarchy rooted at Person.
Also, add some missing Role classes, such as Role, (Organization) Mentor,
(Club) Member, (School) Student. Make (Organization) Administrator be a
Reviewer like Mentor is.
Patch by: Todd Larsen
Review by: Pawel Solyga, Sverre Rabbelier, Augie Fackler
Review URL: http://codereviews.googleopensourceprograms.com/607
release: "1.1.3"
timestamp: 1220920355
api_versions: ['1']