fix(bundles): remove SFX bundle

Closes #5665

BREAKING CHANGE:

The existing sfx bundle (angular2.sfx.dev.js) is replaced by UMD bundles:
angular2.umd.js and angular2.umd.dev.js. The new UMD bundles dont have
polyfills (zone.js, reflect-metadata) pre-appended. Those polyfills
can be easily loaded by including the angular-polyfills.js bundle.

Closes #5712

modules/angular2/angular2_sfx.dart

@@ -1,3 +0,0 @@
-library angular2.sfx;
-
-// empty as we don't have a version for Dart

modules/angular2/angular2_sfx.ts

@@ -1,22 +0,0 @@
-import * as ng from './angular2';
-// the router and http should have their own SFX bundle
-// But currently the module arithmetic 'angular2/router_sfx - angular2/angular2',
-// is not support by system builder.
-import * as router from './router';
-import * as http from './http';
-
-var _prevNg = (<any>window).ng;
-
-(<any>window).ng = ng;
-
-
-(<any>window).ngRouter = router;
-(<any>window).ngHttp = http;
-/**
- * Calling noConflict will restore window.angular to its pre-angular loading state
- * and return the angular module object.
- */
-(<any>ng).noConflict = function() {
-  (<any>window).ng = _prevNg;
-  return ng;
-};