Enable checkstyle Javadoc Comment Style rule

Turn on the Javadoc Comment Style rule and fix
any violations that come up.  This is related to
requiring javadoc description comments to end
with a '.'

Change-Id: I19cf1b9f00d3040987e0b4c8b39461e2e0ad66b5
diff --git a/src/main/java/net/onrc/onos/core/topology/SwitchEvent.java b/src/main/java/net/onrc/onos/core/topology/SwitchEvent.java
index 7ed65d8..36cf8cf 100644
--- a/src/main/java/net/onrc/onos/core/topology/SwitchEvent.java
+++ b/src/main/java/net/onrc/onos/core/topology/SwitchEvent.java
@@ -3,9 +3,9 @@
 import java.nio.ByteBuffer;
 
 /**
- * Self-contained Switch Object
+ * Self-contained Switch Object.
  * <p/>
- * TODO: We probably want common base class/interface for Self-Contained Event Object
+ * TODO: We probably want common base class/interface for Self-Contained Event Object.
  */
 public class SwitchEvent {
     protected final Long dpid;