Adding device type

Adding device type on port(eg Ethernet Port,TPort,WPort), Link(Ethernet,Optical..) and Switch(Ethernet,Optical)
Updated Serializers.
Fixed javadoc issue for Enums.

ONOS-1428

Change-Id: Id3e3094f1fbf90154fff9a61e3c0ca36be69c281
diff --git a/src/main/java/net/onrc/onos/core/topology/LinkImpl.java b/src/main/java/net/onrc/onos/core/topology/LinkImpl.java
index dea629e..5886c8e 100644
--- a/src/main/java/net/onrc/onos/core/topology/LinkImpl.java
+++ b/src/main/java/net/onrc/onos/core/topology/LinkImpl.java
@@ -83,6 +83,17 @@
         return this.topology.getLinkEvent(id).getCapacity();
     }
 
+    /**
+     * Returns the link type of the link.
+     *
+     * @return {@link net.onrc.onos.core.topology.LinkType} for this link
+     */
+    @Override
+    public LinkType getLinkType() {
+        return LinkType.valueOf(getStringAttribute(TopologyElement.ELEMENT_TYPE,
+                LinkType.ETHERNET_LINK.toString()));
+    }
+
     @Override
     public String getStringAttribute(String attr) {
         return this.topology.getLinkEvent(id).getStringAttribute(attr);