Enable REST to manage devices under a proxy

This commit integrates the REST proxy within the standard REST
protocol and provider, supporting multiple devices managed by
a single REST end point (e.g. a REST-based second level controller).

It introduces the concept of RestSBServer, that represents
the REST service exposed by a single or a set of devices.

Change-Id: I0b187151848c20bc1fd8c39a33d57a500f667533
diff --git a/core/api/src/main/java/org/onosproject/net/behaviour/DevicesDiscovery.java b/core/api/src/main/java/org/onosproject/net/behaviour/DevicesDiscovery.java
new file mode 100644
index 0000000..6c553aa
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+++ b/core/api/src/main/java/org/onosproject/net/behaviour/DevicesDiscovery.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2017-present 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.behaviour;
+
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.device.DeviceDescription;
+import org.onosproject.net.driver.HandlerBehaviour;
+
+import java.util.Set;
+
+/**
+ * Handler behaviour capable of managing a set of forwarding plane devices.
+ */
+public interface DevicesDiscovery extends HandlerBehaviour {
+
+    /**
+     * Returns a set of proxied device ids.
+     *
+     * @return a set of deviceId
+     */
+    Set<DeviceId> deviceIds();
+
+    /**
+     * Returns a device description appropriately annotated to support
+     * downstream model extension via projections of the resulting device,
+     * as in the following example.
+     * This process permits to discovery the description of a proxied device by
+     * leveraging on the device ids discovered
+     * @see org.onosproject.net.behaviour.DevicesDiscovery#deviceDetails(DeviceId)
+     *
+     * @param deviceId the device Id of the device of interest
+     * @return annotated device description
+     */
+    DeviceDescription deviceDetails(DeviceId deviceId);
+}
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