[ONOS-7003] Policer implementation

Changes:
- Introduce trafficcontrol package
- Add policer
- Add policer id
- Add policing resource
- Add token bucket
- Add unit tests

Change-Id: I70065d58d3df7033e67a81943ebf60187c33c3e2
diff --git a/core/api/src/main/java/org/onosproject/net/behaviour/trafficcontrol/PolicerId.java b/core/api/src/main/java/org/onosproject/net/behaviour/trafficcontrol/PolicerId.java
new file mode 100644
index 0000000..c373dbe
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/behaviour/trafficcontrol/PolicerId.java
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * 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.trafficcontrol;
+
+
+import com.google.common.annotations.Beta;
+import org.onlab.util.Identifier;
+
+import java.net.URI;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Unique identifier for an ONOS Policer {@link org.onosproject.net.behaviour.trafficcontrol.Policer}.
+ * It uniquely identifies a Policer in the scope of a single device inside ONOS. There may not be any
+ * correspondence with the identifiers of the technology implementing the Policer in the device.
+ * Mapping (if necessary) is left to the specific implementation.
+ */
+@Beta
+public final class PolicerId extends Identifier<String> {
+
+    /**
+     * Represents either no id, or an unspecified id.
+     */
+    public static final PolicerId NONE = policerId("none:none");
+
+    private static final int POLICER_ID_MAX_LENGTH = 1024;
+
+    private final URI uri;
+
+    // Not allowed
+    private PolicerId(URI u) {
+        super(u.toString());
+        uri = u;
+    }
+
+    // Needed for serialization
+    private PolicerId() {
+        super();
+        uri = null;
+    }
+
+    /**
+     * Creates a policer id using the supplied URI.
+     *
+     * @param uri policer id URI
+     * @return PolicerId
+     */
+    public static PolicerId policerId(URI uri) {
+        return new PolicerId(uri);
+    }
+
+    /**
+     * Creates a policer id using the supplied URI string.
+     *
+     * @param string policer id URI string
+     * @return PolicerID
+     */
+    public static PolicerId policerId(String string) {
+        checkArgument(string.length() <= POLICER_ID_MAX_LENGTH,
+                      "URI string exceeds maximum length " + POLICER_ID_MAX_LENGTH);
+        return policerId(URI.create(string));
+    }
+
+    /**
+     * Returns the backing URI.
+     *
+     * @return backing URI
+     */
+    public URI uri() {
+        return uri;
+    }
+
+}