PortNumber fixes

- hide new PortNumber(short) and use PortNumber.uint16 instead
- added utility to get PortNumber

Change-Id: Ia39fbe6e7126a3d9465d3035a06850c1d54a7f25
diff --git a/src/main/java/net/onrc/onos/apps/sdnip/Interface.java b/src/main/java/net/onrc/onos/apps/sdnip/Interface.java
index 463cac8..4052e81 100644
--- a/src/main/java/net/onrc/onos/apps/sdnip/Interface.java
+++ b/src/main/java/net/onrc/onos/apps/sdnip/Interface.java
@@ -73,7 +73,7 @@
     public SwitchPort getSwitchPort() {
         //TODO SwitchPort, Dpid and Port are mutable, but they could probably
         //be made immutable which would prevent the need to copy
-        return new SwitchPort(new Dpid(dpid), new PortNumber(port));
+        return new SwitchPort(new Dpid(dpid), PortNumber.uint16(port));
     }
 
     /**