Added endPortA/B to UiLink class.
Removed 'online' property from UiDevice, choosing to look up availability on the fly from device service.

Change-Id: Ib14ab371a11c442a30cf407f11d366271d087c68
diff --git a/core/api/src/main/java/org/onosproject/ui/model/topo/UiDeviceLink.java b/core/api/src/main/java/org/onosproject/ui/model/topo/UiDeviceLink.java
index 4575678..3eaa827 100644
--- a/core/api/src/main/java/org/onosproject/ui/model/topo/UiDeviceLink.java
+++ b/core/api/src/main/java/org/onosproject/ui/model/topo/UiDeviceLink.java
@@ -59,6 +59,16 @@
         return deviceB + UiLinkId.ID_PORT_DELIMITER + portB;
     }
 
+    @Override
+    public String endPortA() {
+        return portA.toString();
+    }
+
+    @Override
+    public String endPortB() {
+        return portB.toString();
+    }
+
 
     @Override
     protected void destroy() {