Add skeletal code for control message provider

Change-Id: I29e28ae268693f62631f2d70a5e6f74e482a4643
diff --git a/providers/openflow/pom.xml b/providers/openflow/pom.xml
index 530f6f8..af38b0b 100644
--- a/providers/openflow/pom.xml
+++ b/providers/openflow/pom.xml
@@ -39,6 +39,9 @@
         <module>meter</module>
         <module>base</module>
         <module>app</module>
+
+        <!-- optional -->
+        <module>message</module>
     </modules>
 
     <dependencies>