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/core/newintent/SingleDstTreeFlowIntent.java b/src/main/java/net/onrc/onos/core/newintent/SingleDstTreeFlowIntent.java
index 498eb0a..3c7a365 100644
--- a/src/main/java/net/onrc/onos/core/newintent/SingleDstTreeFlowIntent.java
+++ b/src/main/java/net/onrc/onos/core/newintent/SingleDstTreeFlowIntent.java
@@ -29,6 +29,14 @@
     }
 
     /**
+     * Constructor for serializer.
+     */
+    protected SingleDstTreeFlowIntent() {
+        super();
+        this.tree = null;
+    }
+
+    /**
      * Returns the tree.
      *
      * @return tree