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/public_api_spec.ts

@@ -140,7 +140,6 @@ var NG_COMPILER = [
 ];
 
 var NG_CORE = [
-  'APP_COMPONENT',
   'APP_INITIALIZER',
   'APP_ID',
   'AngularEntrypoint:dart',
@@ -261,7 +260,12 @@ var NG_CORE = [
   'provide',
   'createNgZone',
   'forwardRef:js',
-  'platform',
+  'coreBootstrap',
+  'coreLoadAndBootstrap',
+  'createPlatform',
+  'disposePlatform',
+  'getPlatform',
+  'assertPlatform',
   'resolveForwardRef:js',
   'PLATFORM_COMMON_PROVIDERS',
   'PLATFORM_INITIALIZER',
@@ -306,6 +310,7 @@ var NG_PLATFORM_BROWSER = [
   'ELEMENT_PROBE_PROVIDERS_PROD_MODE',
   'Title',
   'bootstrap',
+  'browserPlatform',
   'disableDebugTools',
   'enableDebugTools',
   'inspectNativeElement'