Remove Spring WebSocket support

pom.xml

@@ -156,11 +156,6 @@
 			<artifactId>spring-webmvc</artifactId>
 			<version>${org.springframework-version}</version>
 		</dependency>
-		<dependency>
-			<groupId>org.springframework</groupId>
-			<artifactId>spring-websocket</artifactId>
-			<version>${org.springframework-version}</version>
-		</dependency>
 		<!-- Security -->
 		<dependency>
 			<groupId>org.springframework.security</groupId>

src/main/java/de/thm/arsnova/socket/EchoHandler.java

-package de.thm.arsnova.socket;
-
-import org.springframework.web.socket.TextMessage;
-import org.springframework.web.socket.WebSocketSession;
-import org.springframework.web.socket.handler.TextWebSocketHandler;
-
-public class EchoHandler extends TextWebSocketHandler {
-
-  @Override
-  public void handleTextMessage(WebSocketSession session,
-      TextMessage message) throws Exception {
-
-    session.sendMessage(message);
-  }
-
-}

src/main/java/de/thm/arsnova/socket/WebSocketConfig.java

-package de.thm.arsnova.socket;
-
-import org.springframework.context.annotation.Configuration;
-import org.springframework.web.socket.config.annotation.EnableWebSocket;
-import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
-import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
-
-@Configuration
-@EnableWebSocket
-public class WebSocketConfig implements WebSocketConfigurer {
-
-	@Override
-	public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
-		registry.addHandler(new EchoHandler(), "/socket/echo");
-	}
-
-}