refactor(WebWorker): Make WebWorker bootstrap synchronous

BREAKING CHANGE

From the app thread, in both TypeScript and Dart, you bootstrap the app
using `application` instead of `asyncApplication`.
Before:
```TypeScript
platform([WORKER_APP_PLATFORM])
.asyncApplication(setupWebWorker, optionalProviders?)
.then((ref) => ref.bootstrap(RootComponent));
```
Now:
```TypeScript
platform([WORKER_APP_PLATFORM])
.application([WORKER_APP_APPLICATION])
.bootstrap(RootComponent);
```

closes #5857

Closes #5862

modules/angular2/src/web_workers/debug_tools/multi_client_server_message_bus.dart

@@ -84,7 +84,7 @@ class WebSocketWrapper {
     _socket.addStream(_sendStream.stream);
   }
 
-  void send (String data) {
+  void send(String data) {
     _sendStream.add(data);
   }