Metamodel: Add parseEnumerationReference() and parseEnumerationReferences() to Metamodel so we can read annotation classes whose parameters are enumerated cases. See ceylon/ceylon-compiler#1245
Add @EnumerationReference, an annotation on annotation type methods of type java.lang.Class, to note that in Ceylon terms they are serializing an anonymous class that's a case of some enumerated type.

Add @DefaultedObject, to record the default value of a defaulted annotation constructor parameter that is an anonymous class that's a case of some enumerated type.

See ceylon/ceylon-compiler#1245