REST tool improvements

The following improvement should be considered:

• Add support for exposing complex child nodes / references if they are XML-annotated as well.
• Provide a way to XML-annotate new fields (after adding a new document type field in the CMS, you can run bean re-generation, but this will not, currently, XML-annotate your new getter, even if other getters in the bean are annotated.
• Support the retrieval of individual documents, rather than (queried) lists of documents.
• REST services configuration tool does not provide feedback about already existing REST services, i.e. if you configure them, rebuild and go back, there's nothing there telling you that you've already done so. Also, the handy links for testing are no longer available. If you happen to try to add the same rest endpoint again, the backend throws an exception (stacktrace in the terminal).