Sketching out what link-state addition would look like; quite easy until we get to the distributed store.
Added unit tests to provide durable-nondurable transitions.
FIxed issue where link could be accidentally activated.
Renamed parameter.

Change-Id: I8aa19a6583ec50dbf28769995f0a8ea9be9a4daa
diff --git a/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java b/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java
index b164b9e..763e95e 100644
--- a/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/link/LinkEvent.java
@@ -33,7 +33,7 @@
         LINK_ADDED,
 
         /**
-         * Signifies that a link has been updated.
+         * Signifies that a link has been updated or changed state.
          */
         LINK_UPDATED,