Add a sent_id to the UD Converter, since the validation script used in UD tools seems to throw a fit over not having a sent_id

Author: AngledLuffa

src/edu/stanford/nlp/trees/ud/UniversalDependenciesConverter.java

@@ -329,6 +329,7 @@ public static void main(String[] args) {
         }
         addSpaceAfter(sg, text, graphIdx);
       }
+      System.out.println("# sent_id = " + graphIdx);
       System.out.print(writer.printSemanticGraph(sg, enhanced));
       ++graphIdx;
     }