BACM — Rewrite section 7.2.2 for clarification

The prose of this section is difficult to understand. It needs to explain how an instance of a class can be a class and how individuals are represented as singleton sets. It is unclear that the singleton set interpretation can be imposed in the MOF model without a change to the metamodel to add an Individual abstract metaclass that is specialized by the MOF classes resulting from the translation of <<individual>> stereotyped EA classes.