Implement serialization/deserialization feature for each Intent classes

Change-Id: I63db34914d8df76d5a000831da1e03e03383e62f
diff --git a/src/main/java/net/onrc/onos/intent/Intent.java b/src/main/java/net/onrc/onos/intent/Intent.java
index 823b106..070af25 100644
--- a/src/main/java/net/onrc/onos/intent/Intent.java
+++ b/src/main/java/net/onrc/onos/intent/Intent.java
@@ -13,6 +13,8 @@
 	public String getId() {
 		return id;
 	}
+	
+	abstract public byte[] toBytes();
 
 	@Override
 	public int hashCode() {