Add how to ignore namespace (#552)

To ignore the namepace it has to be set to null.
The @description describes how to set to null using the flux. The method
description describes how to set it using the JAVA-API.

metafacture-biblio/src/main/java/org/metafacture/biblio/marc21/MarcXmlHandler.java

@@ -32,7 +32,7 @@
  * @author Markus Michael Geipel
  *
  */
-@Description("A marc xml reader")
+@Description("A MARC XML reader. To read marc data without namespace specification set option `namespace=\"\"`")
 @In(XmlReceiver.class)
 @Out(StreamReceiver.class)
 @FluxCommand("handle-marcxml")
@@ -63,7 +63,7 @@ public MarcXmlHandler() {
      *
      * <strong>Default value: {@value #NAMESPACE}</strong>
      *
-     * @param namespace the namespace
+     * @param namespace the namespace. Set to null if namespace shouldn't be checked.
      */
     public void setNamespace(final String namespace) {
         this.namespace = namespace;