Cleaned up warnings reported by the Javadoc tool.

Javadoc reports warnings for things such as missing return descriptions,
missing or wrong parameters, invalid tags.

Note: I didn't touch any of the warnings in the OpenflowJ code.

Change-Id: I7234f617e092b489fad599196fc9cbe78f7e2db1
diff --git a/src/main/java/net/floodlightcontroller/core/IListener.java b/src/main/java/net/floodlightcontroller/core/IListener.java
index 74ff1f3..17925a5 100644
--- a/src/main/java/net/floodlightcontroller/core/IListener.java
+++ b/src/main/java/net/floodlightcontroller/core/IListener.java
@@ -25,7 +25,7 @@
     /**
      * The name assigned to this listener
      *
-     * @return
+     * @return the name of the listener
      */
     public String getName();