RDF'ed serialization

The pattern looks good, but each serialization in this for-loop should provide its own details. Your implementation is hard-coded for jcr/xml serialization.

The variable "jcrXML" should probably be:
```
createResource(REPOSITORY_NAMESPACE + <key>);
```

Each "serializer" should provide its own "label" (i.e. "JCR/XML").
The subject (formatJcrXML) in the final model.add() should be the "format" resource.