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/PathIntent.java b/src/main/java/net/onrc/onos/api/newintent/PathIntent.java
index db11f4c..5b9a42f 100644
--- a/src/main/java/net/onrc/onos/api/newintent/PathIntent.java
+++ b/src/main/java/net/onrc/onos/api/newintent/PathIntent.java
@@ -37,6 +37,11 @@
         this.path = ImmutableList.copyOf(checkNotNull(path));
     }
 
+    protected PathIntent() {
+        super();
+        this.path = null;
+    }
+
     /**
      * Returns the links which the traffic goes along.
      *