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?
```
/**
 * Returns the document ID
 * @return the document ID
 */