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/SwitchType.java b/src/main/java/net/onrc/onos/core/topology/SwitchType.java
new file mode 100644
index 0000000..062a7ee
--- /dev/null
+++ b/src/main/java/net/onrc/onos/core/topology/SwitchType.java
@@ -0,0 +1,5 @@
+package net.onrc.onos.core.topology;
+
+public enum SwitchType {
+    ETHERNET_SWITCH, OPTICAL_SWITCH;
+}