Included connect point port number in definition of UiLinkId.
Added dumpString() to ModelCache / UiTopology.
Added more unit tests for ModelCache.

Change-Id: I842bb418b25cc901bd12bc28c6660c836f7235bc
diff --git a/core/api/src/main/java/org/onosproject/ui/model/topo/UiDevice.java b/core/api/src/main/java/org/onosproject/ui/model/topo/UiDevice.java
index bb59752..3ed9da0 100644
--- a/core/api/src/main/java/org/onosproject/ui/model/topo/UiDevice.java
+++ b/core/api/src/main/java/org/onosproject/ui/model/topo/UiDevice.java
@@ -87,6 +87,16 @@
     }
 
     /**
+     * Returns the identifier of the region to which this device belongs.
+     * This will be null if the device does not belong to any region.
+     *
+     * @return region identity
+     */
+    public RegionId regionId() {
+        return regionId;
+    }
+
+    /**
      * Returns the UI region to which this device belongs.
      *
      * @return the UI region