refactor(core): support non reflective bootstrap.

This changes Angular so that it can be used without reflection (assuming a codegen for injectors).

BREAKIKNG CHANGE:
- Drops `APP_COMPONENT` provider. Instead, inject
  `ApplicationRef` and read its `componentTypes` property.
- long form bootstrap has changed into the following:
  ```
  var platform = createPlatform(ReflectiveInjector.resolveAndCreate(BROWSER_PROVIDERS));
  var appInjector =
    ReflectiveInjector.resolveAndCreate([BROWSER_APP_PROVIDERS, appProviders], platform.injector);
  coreLoadAndBootstrap(appInjector, MyApp);
  ```

modules/angular2/test/web_workers/debug_tools/bootstrap.server.spec.dart

@@ -19,8 +19,11 @@ main() {
     it("should be able to load in a Dart VM", () {
       reflector.reflectionCapabilities = new ReflectionCapabilities();
       var buses = createPairedMessageBuses();
-      platform([WORKER_APP_PLATFORM])
-          .application([WORKER_APP_APPLICATION_COMMON]);
+      disposePlatform();
+      var platform = createPlatform(ReflectiveInjector.resolveAndCreate(WORKER_APP_PLATFORM));
+      var appInjector = ReflectiveInjector.resolveAndCreate(WORKER_APP_APPLICATION_COMMON,
+          platform.injector);
+      appInjector.get(ApplicationRef);
     });
   });
 }