Add more checkstyle tests

- Lines containing tab(s) after space
- Usage of printStackTrace
- Usage of println
- Add SupressionCommentFilter module

SuppressionCommentFilter can be enabled with
// CHECKSTYLE:OFF
and disabled with
// CHECKSTYLE:ON

smack-extensions/src/main/java/org/jivesoftware/smackx/pubsub/Item.java

@@ -85,7 +85,9 @@ public class Item extends NodeExtension
 	 */
     public Item(String itemId, String nodeId) 
     {
+    // CHECKSTYLE:OFF
     	super(PubSubElementType.ITEM_EVENT, nodeId);
+    // CHECKSTYLE:ON
         id = itemId;
     }