GH-340: Fix logging for WebSocket server side

Fixes https://github.com/spring-projects/spring-integration-samples/issues/340

The `LoggingHandler` uses a `org.springframework.integration.handler` category by default.
So, the `info` provided for the `loggingChannelAdapter` service activator does not
have any effects because `logback.xml` has an `ERROR` for the
`org.springframework.integration` category

* Use dedicated `wsLog` category in the `LoggingHandler` bean definition
to print a server message published to the subscribed web socket clients

basic/web-sockets/src/main/java/org/springframework/integration/samples/websocket/standard/server/Application.java

@@ -128,6 +128,7 @@ public class Application {
 	@ServiceActivator(inputChannel = "sendTimeChannel")
 	public MessageHandler loggingChannelAdapter() {
 		LoggingHandler loggingHandler = new LoggingHandler("info");
+		loggingHandler.setLoggerName("wsLog");
 		loggingHandler.setLogExpressionString(
 				"'The time ' + payload + ' has been sent to the WebSocketSession ' + headers.simpSessionId");
 		return loggingHandler;