Support Kryo serialization for intent related types

- Implement the protected constructors
- Register the types in KryoFactory

Change-Id: I14214ed1703a8e4b3145625732c74600fc0aba06
diff --git a/src/main/java/net/onrc/onos/api/newintent/IntentEvent.java b/src/main/java/net/onrc/onos/api/newintent/IntentEvent.java
index 670e87e..3dcf2a8 100644
--- a/src/main/java/net/onrc/onos/api/newintent/IntentEvent.java
+++ b/src/main/java/net/onrc/onos/api/newintent/IntentEvent.java
@@ -33,6 +33,16 @@
     }
 
     /**
+     * Constructor for serializer.
+     */
+    protected IntentEvent() {
+        this.intent = null;
+        this.state = null;
+        this.previous = null;
+        this.time = 0;
+    }
+
+    /**
      * Returns the state of the intent which caused the event.
      *
      * @return the state of the intent