Refactored tunnel and interface config behavior

- Added tunnel interface configuratoin to interfaceConfig and
  deprecated tunnelConfig
- OVSDB client service provides interface create/remove APIs instead
  of tunnel interface create/remove, and this APIs can be used to
  create/remove various types of interfaces like tunnel, patch, tap and so on
- Use tunnel description when create tunnel interface so that we can extend
  more config options later
- Some cleaup OVSDB client

Change-Id: I4653595504a27b18384a92ebe4b31ce9d99237cd
diff --git a/core/api/src/main/java/org/onosproject/net/behaviour/TunnelKeys.java b/core/api/src/main/java/org/onosproject/net/behaviour/TunnelKeys.java
new file mode 100644
index 0000000..4b98064
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/behaviour/TunnelKeys.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2016-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;
+
+/**
+ * Static utility methods pertaining to {@link TunnelKey} instances.
+ */
+public final class TunnelKeys {
+
+    private TunnelKeys() {
+    }
+
+    private static TunnelKey<String> flowKey = new TunnelKey<>("flow");
+
+    /**
+     * Returns a tunnel key with FLOW keyword.
+     *
+     * @return tunnel key instance
+     */
+    public static TunnelKey<String> flowTunnelKey() {
+        return flowKey;
+    }
+
+    // TODO add more for various types of tunnel
+}