API definitions for the TE Topology Core App.

This APP creates and manages a hierarchy of TE topologies received from SBI TE provider and from user configurations from NBI.
The API contains internal data structures for TE attributes that are aligned with the TE attributes definition in standard IETF YANG TE topology model (https://tools.ietf.org/html/draft-ietf-teas-yang-te-topo-05).

This commit includes the following interface definitions:
- TE topology provider service, which is called by the TE topology provider from SB to pass TE topologies to the TE topology core APP
- TE topology service, which provides service APIs for an external APP to get/set TE topologies and their attributes.
- Network, Node, Link definitions for TE networks and their default class implementation

Change-Id: Iafcf6911b8d9e494397e3a255cae282bbca74d5c
diff --git a/apps/tetopology/src/main/java/org/onosproject/tetopology/management/api/DefaultNetworks.java b/apps/tetopology/src/main/java/org/onosproject/tetopology/management/api/DefaultNetworks.java
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@@ -0,0 +1,95 @@
+/*
+ * 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.tetopology.management.api;
+
+import java.util.List;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.base.Objects;
+
+/**
+ * Default Networks implementation.
+ * <p>
+ * The Set/Get methods below are defined to accept and pass references because
+ * the object class is treated as a "composite" object class that holds
+ * references to various member objects and their relationships, forming a
+ * data tree. Internal routines of the TE topology manager may use the
+ * following example methods to construct and manipulate any piece of data in
+ * the data tree:
+ * <pre>
+ * newNode.getTe().setAdminStatus(), or
+ * newNode.getSupportingNodeIds().add(nodeId), etc.
+ * </pre>
+ * Same for constructors where, for example, a child list may be constructed
+ * first and passed in by reference to its parent object constructor.
+ */
+public class DefaultNetworks implements Networks, TeTopologyEventSubject {
+    private List<Network> networks;
+
+    /**
+     * Creates an instance of DefaultNetworks.
+     */
+    public DefaultNetworks() {
+    }
+
+    /**
+     * Constructor with all fields.
+     *
+     * @param networks list of networks
+     */
+    public DefaultNetworks(List<Network> networks) {
+        this.networks = networks;
+    }
+
+    @Override
+    public List<Network> networks() {
+        return networks;
+    }
+
+    /**
+     * Sets the networks.
+     *
+     * @param networks the networks to set
+     */
+    public void setNetworks(List<Network> networks) {
+        this.networks = networks;
+    }
+
+    @Override
+    public int hashCode() {
+       return Objects.hashCode(networks);
+    }
+
+    @Override
+    public boolean equals(Object object) {
+        if (this == object) {
+            return true;
+        }
+        if (object instanceof DefaultNetworks) {
+            DefaultNetworks that = (DefaultNetworks) object;
+            return Objects.equal(this.networks, that.networks);
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(this)
+                .add("networks", networks)
+                .toString();
+    }
+
+}