MOF14 — Add 'semantics' attribute to Operation.

At the moment MOF has no way to describe the behavior of an operation. A new attribute, 'semantics', String (0..1) should be added to Operation. A more sophisticated alternative would be to include a 'language' attribute also, as for Constraint. This would be somewhat restrictive in permitting only one coding of the semantics (e.g. not both OCL and Java). Better would be to use just one multivalued attribute of type StructuredDataType 'Expression'. This would be as in UML and have StructureFields 'language' (String 0..1) and 'body' (String 1..1). It begs the question as to whether this datatype should then be used in Constraint instead of the current 'language' and 'expression' attributes.