Remove methods which expose internal ID

Remove the following methods with expose internal IDs
from public view

- DatastoreExtended#getDocNumericId() - Removed from public interface
- BasicDocumentRevision#getInternalNumericId() - Changed visibiity to protected

Only one question, should the getDocNumericId on BasicDatastore remain public or be made protected?
This should follow the javadoc on BasicDocumentRevision, but just mention documents, not revisions:

``
   /**
     * <p>Returns the internal numeric ID of this document revision.</p>
     *
     * @return  the internal numeric ID of this document.
     */
``