Use SerialVersionUID 200L (version 2.0.0).
Rework core serialization:
- all Content is 'detached' now after serialization (but Element and Document re-attache where required on deserialization).
- Namespace is now serializable
Remove the 'new' JDOMRuntimeException, replace it with core Java Illegal*Exceptions.
Add serialization tests to Filter classes. Filters are still serializable, not sure why that is needed.
Fiox up some code coverage tests.... including complicated 'Bridge Methods' for co-variant return-type bridge methods.