Fix some checkstyle and PMD errors in the topology module.

Change-Id: Icf037cefdff18256f1234ed2b6eac761d29af7ac
diff --git a/src/main/java/net/onrc/onos/core/topology/web/serializers/PortSerializer.java b/src/main/java/net/onrc/onos/core/topology/web/serializers/PortSerializer.java
index 628a923..ff08f5b 100644
--- a/src/main/java/net/onrc/onos/core/topology/web/serializers/PortSerializer.java
+++ b/src/main/java/net/onrc/onos/core/topology/web/serializers/PortSerializer.java
@@ -10,8 +10,14 @@
 import org.codehaus.jackson.map.SerializerProvider;
 import org.codehaus.jackson.map.ser.std.SerializerBase;
 
+/**
+ * Serializes a Port object as JSON.
+ */
 public class PortSerializer extends SerializerBase<Port> {
 
+    /**
+     * Constructs a Port serializer.
+     */
     public PortSerializer() {
         super(Port.class);
     }