Detangling incubator: virtual nets, tunnels, resource labels, oh my

- virtual networking moved to /apps/virtual; with CLI & REST API
- tunnels and labels moved to /apps/tunnel; with CLI & REST API; UI disabled for now
- protobuf/models moved to /core/protobuf/models
- defunct grpc/rpc registry stuff left under /graveyard
- compile dependencies on /incubator moved to respective modules for compilation
- run-time dependencies will need to be re-tested for dependent apps

- /graveyard will be removed in not-too-distant future

Change-Id: I0a0b995c635487edcf95a352f50dd162186b0b39
diff --git a/apps/tunnel/api/src/main/java/org/onosproject/incubator/net/domain/IntentDomainId.java b/apps/tunnel/api/src/main/java/org/onosproject/incubator/net/domain/IntentDomainId.java
new file mode 100644
index 0000000..5140762
--- /dev/null
+++ b/apps/tunnel/api/src/main/java/org/onosproject/incubator/net/domain/IntentDomainId.java
@@ -0,0 +1,53 @@
+/*
+ * Copyright 2018-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.incubator.net.domain;
+
+import com.google.common.annotations.Beta;
+import org.onlab.util.Identifier;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Intent domain identifier.
+ */
+@Beta
+public class IntentDomainId extends Identifier<String> {
+    /**
+     * Creates an intent domain identifier from the specified string representation.
+     *
+     * @param value string value
+     * @return intent identifier
+     */
+    public static IntentDomainId valueOf(String value) {
+        return new IntentDomainId(value);
+    }
+
+    /**
+     * Constructor for serializer.
+     */
+    IntentDomainId() {
+        super(null);
+    }
+
+    /**
+     * Constructs the ID corresponding to a given string value.
+     *
+     * @param value the underlying value of this ID
+     */
+    IntentDomainId(String value) {
+        super(checkNotNull(value, "Intent domain ID cannot be null."));
+    }
+}