unsigned PortNumber

PortNumber class update
- internal representation now uses int
- toString() now converts the value as unsigned integer
- renamed value() to shortValue()
- added value() method returning port number as unsigned long
- added constructor from String
- JSON serialization now uses the new value(), so that special handling for
  unsigned integer is not required

Update classes using PortNumber
- Replaced value() calls with new value(), when the return value was
  converted to long immediately.
- toString() result may change if the object contained PortNumber.
  - e.g., FlowEntryAction, FlowEntry, SwitchPort, ...

Change-Id: I0b1f8aa92208e165b6113c8dd6954076c0513167
diff --git a/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java b/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java
index 48c3b65..1c01e8f 100644
--- a/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java
+++ b/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java
@@ -48,7 +48,7 @@
      */
     @Test
     public void testToString() {
-        assertEquals("00:00:00:00:00:00:00:01/-1", SWP2.toString());
+        assertEquals("00:00:00:00:00:00:00:01/65535", SWP2.toString());
     }
 
     /**