[ONOS-5070] Adds mirroring functionality.

Changes:
- Adds mirroring behaviour;
- Adds mirroring description;
- Adds mirroring name;
- Implements for Ovsdb the mirroring;
- Adds OvsdbMirror entity;
- Adds constants related to Mirror table;
- Fix one issue related to Mirror table
- Extends OvsdbClientService introducing mirroring;
- Implements mirroring functionality in DefaulOvsdbClient;
- Support for different types of device id

Change-Id: Ie291f49b3c61b7998010f555ae11deb8c021063d
diff --git a/protocols/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbConstant.java b/protocols/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbConstant.java
index 6562384..aea0845 100644
--- a/protocols/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbConstant.java
+++ b/protocols/ovsdb/api/src/main/java/org/onosproject/ovsdb/controller/OvsdbConstant.java
@@ -41,6 +41,7 @@
     /** Bridge table. */
     public static final String BRIDGE = "Bridge";
     public static final String PORTS = "ports";
+    public static final String MIRRORS = "mirrors";
     // other configs
     public static final String DATAPATH_ID = "datapath-id";
     public static final String DISABLE_INBAND = "disable-in-band";
@@ -66,6 +67,9 @@
     /** Controller table. */
     public static final String CONTROLLER = "Controller";
 
+    /** Mirror table. */
+    public static final String MIRROR = "Mirror";
+
     /** Ovsdb bridge name. */
     // TODO remove this particular bridge name from OVSDB provider
     public static final String INTEGRATION_BRIDGE = "br-int";