TE Topoplogy subsystem I2RS API changes

This submission contains the following:

1. Major changes in apps/tetopology. The changes are mainly introduced
   to support new searching keys in TE Topology.

2. Add RESTCONF notification support in the TE Provider. i.e., for
   south-bound RESTCONF communication with the domain controller.

Change-Id: I6786959deb66c98626edc65ff52694dcf08981a3
diff --git a/apps/tetopology/api/src/main/java/org/onosproject/tetopology/management/api/link/PathElement.java b/apps/tetopology/api/src/main/java/org/onosproject/tetopology/management/api/link/PathElement.java
new file mode 100644
index 0000000..e5158f7
--- /dev/null
+++ b/apps/tetopology/api/src/main/java/org/onosproject/tetopology/management/api/link/PathElement.java
@@ -0,0 +1,113 @@
+/*
+ * 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.link;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.base.Objects;
+
+/**
+ * Representation of a path element.
+ */
+public class PathElement {
+    private final long pathElementId;
+    private final long teNodeId;
+    private final ElementType type;
+    private final boolean loose;
+
+    /**
+     * Creates a path element.
+     *
+     * @param pathElementId path element identifier
+     * @param teNodeId      identifier of the TE node to which this
+     *                      path element belongs
+     * @param type          path element type
+     * @param loose         loose if true; strict if false
+     */
+    public PathElement(long pathElementId, long teNodeId,
+                       ElementType type, boolean loose) {
+        this.pathElementId = pathElementId;
+        this.teNodeId = teNodeId;
+        this.type = type;
+        this.loose = loose;
+    }
+
+    /**
+     * Returns the path element identifier.
+     *
+     * @return path element id
+     */
+    public long pathElementId() {
+        return pathElementId;
+    }
+
+    /**
+     * Returns the TE node identifier.
+     *
+     * @return te node id
+     */
+    public long teNodeId() {
+        return teNodeId;
+    }
+
+    /**
+     * Returns the path element type.
+     *
+     * @return path element type
+     */
+    public ElementType type() {
+        return type;
+    }
+
+    /**
+     * Returns the loose flag. true = loose; false = strict.
+     *
+     * @return loose value
+     */
+    public boolean loose() {
+        return loose;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(pathElementId, teNodeId, type, loose);
+    }
+
+    @Override
+    public boolean equals(Object object) {
+        if (this == object) {
+            return true;
+        }
+        if (object instanceof PathElement) {
+            PathElement that = (PathElement) object;
+            return Objects.equal(pathElementId, that.pathElementId) &&
+                    Objects.equal(teNodeId, that.teNodeId) &&
+                    Objects.equal(type, that.type) &&
+                    Objects.equal(loose, that.loose);
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(this)
+                .add("pathElementId", pathElementId)
+                .add("teNodeId", teNodeId)
+                .add("type", type)
+                .add("loose", loose)
+                .toString();
+    }
+
+}