Introducing concept of a physical or logical region to facilitate
support of geographically distributed cluster and to lay ground
for multiple/filtered topology layouts.

Added implementation of manager and store; unit-tests included.

Change-Id: Ia01673a0b711b8785c0ea68768552c2f61d7ea6d
diff --git a/core/api/src/main/java/org/onosproject/net/region/RegionId.java b/core/api/src/main/java/org/onosproject/net/region/RegionId.java
new file mode 100644
index 0000000..0754f6e
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/region/RegionId.java
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2016 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.region;
+
+import org.onlab.util.Identifier;
+
+/**
+ * Region identifier backed by a string value.
+ */
+public final class RegionId extends Identifier<String> {
+
+    /**
+     * Constructor for serialization.
+     */
+    private RegionId() {
+        super();
+    }
+
+    /**
+     * Constructs the ID corresponding to a given string value.
+     *
+     * @param value the underlying value of this ID
+     */
+    private RegionId(String value) {
+        super(value);
+    }
+
+    /**
+     * Creates a new region identifier.
+     *
+     * @param id backing identifier value
+     * @return region identifier
+     */
+    public static RegionId regionId(String id) {
+        return new RegionId(id);
+    }
+
+}