This class is used within the context of a FactorySpec to express
namespaces that should be either included and/or excluded from source
code generation. The ability to include/exclude specific namespaces from
wsdl2java generation allows certain namespaces to be mapped to custom
bean classes, have wsdl-generated stubs/skeletons declared to pass those
types, and not have the wsdl2java process generate classes which would
conflict with the externally developed custom beans.