Write valid leader without counting #527

Instead of just appending the incoming leader elements, this adds the static values for Pos: 00-04, 10-16, 20-23.

By using `0`as default value for Pos: 00-04 and 12-16.

#527 (comment)

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

@@ -435,7 +435,7 @@ private void writeLeader() {
             if (!leader.isEmpty()) {
                 prettyPrintIndentation();
                 writeTag(Tag.leader::open);
-                writeRaw(leader);
+                writeRaw("0000" + leader.substring(0, 4) + "2200000" + leader.substring(5, 7) + "4500") // creates a valid leader without counted elements
                 writeTag(Tag.leader::close);
                 prettyPrintNewLine();
             }