Initial implementation: The init extended flow rule and store interface APIs

The APIs are for supporting service data to install on network devices.
This is related to JIRA ticket ID ONOS-869.

Updated API code and added implementation code files.

Modified API for supporting payload abstruction, and added routing mechanism for pushing flow rules to devices.
Added more javadoc, and fixed some minor issues.

Updated javadoc, removed unnecessary method, and test code.

Change-Id: I105defc92a9e01b30601fcb56a9dafa086d4adc0
diff --git a/core/api/src/main/java/org/onosproject/net/flowext/FlowRuleExtRouterListener.java b/core/api/src/main/java/org/onosproject/net/flowext/FlowRuleExtRouterListener.java
new file mode 100644
index 0000000..45caee9
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/flowext/FlowRuleExtRouterListener.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.flowext;
+
+import org.onosproject.net.flow.FlowRuleBatchEvent;
+
+/**
+ * Experimental extension to the flow rule subsystem; still under development.
+ * The monitor module of the router.
+ * <p>
+ * The monitor module of router.
+ * </p>
+ */
+public interface FlowRuleExtRouterListener {
+
+    /**
+     * Notify monitor the router has down its work.
+     *
+     * @param event the event to notify
+     */
+    void notify(FlowRuleBatchEvent event);
+}