updated websocket handling

...d/src/main/java/de/vipra/rest/resource/TopicResource.java

vipra-backend/src/main/java/de/vipra/ws/WebSocket.java

vipra-backend/src/main/java/de/vipra/ws/msg/InitMessage.java

...ckend/src/main/java/de/vipra/ws/msg/WebSocketMessage.java

vipra-ui/app/js/config.js

vipra-ui/app/js/controllers.js

vipra-ui/app/js/factories.js

vipra-util/src/main/java/de/vipra/util/MultiMap.java