This is a convenient base class for all classes that wish to establish an initial identity which will be the basis of a one-per vm identity: i.e. in any vm there should only ever be a single object with a given identity token (except transiently during canonicalization) It would be convenient to put the getter/setter methods for the identity token here, but unfortunately we have no way of setting up the for Referenceability in multiple levels of a class hierarchy. So we leave the getters/setters, and variable initialization to code-generators.