Remove download by downloadId functionality (#1820)

This functionallity seems to get via AMQP (after some authentication)
a private (wihtout need of authentication) url to an artifact assigned
to the controller.

By default, DDI or DMF shall provide proper urls (for direct download)
to devices and if they have to be without authentication this shall be
solved in different ways - for instance separate download server providing
dedicated private / signed urls.

This functinallity is not a real hawkBit part but more like something
intended to solve some edge cases.
Since it is complicated, heeds support, doesn't solve wide spread use
cases, and could be achieved with other means - better to be removed.

Signed-off-by: Marinov Avgustin <Avgustin.Marinov@bosch.com>

hawkbit-rest/hawkbit-rest-core/src/main/java/org/eclipse/hawkbit/rest/data/ResponseList.java

@@ -17,11 +17,9 @@ import java.util.ListIterator;
 import org.springframework.hateoas.RepresentationModel;
 
 /**
- * List that extends ResourceSupport to ensure that links in content are in HAL
- * format.
+ * List that extends RepresentationModel to ensure that links in content are in HAL format.
  * 
- * @param <T>
- *            of the response content
+ * @param <T> of the response content
  */
 public class ResponseList<T> extends RepresentationModel<ResponseList<T>> implements List<T> {