Move inner interfaces to upper level to reduce IntentManager's size

Change-Id: Ice4fba9e0e70f72904fe7dfa9f371f61ca739b48
diff --git a/core/net/src/main/java/org/onosproject/net/intent/impl/IntentUpdate.java b/core/net/src/main/java/org/onosproject/net/intent/impl/IntentUpdate.java
new file mode 100644
index 0000000..155c0fe
--- /dev/null
+++ b/core/net/src/main/java/org/onosproject/net/intent/impl/IntentUpdate.java
@@ -0,0 +1,43 @@
+/*
+ * 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.intent.impl;
+
+import org.onosproject.net.intent.BatchWrite;
+
+import java.util.Optional;
+
+/**
+ * Represents a phase of processing an intent.
+ */
+interface IntentUpdate {
+
+    /**
+     * Execute the procedure represented by the instance
+     * and generates the next update instance.
+     *
+     * @return next update
+     */
+    default Optional<IntentUpdate> execute() {
+        return Optional.empty();
+    }
+
+    /**
+     * Write data to the specified BatchWrite before execution() is called.
+     *
+     * @param batchWrite batchWrite
+     */
+    default void writeBeforeExecution(BatchWrite batchWrite) {}
+}