refactor: export core APIs from angular2/core

This change moves many APIs to the angular2/core export.

This change also automatically adds FORM_BINDINGS in
the application root injector.

BREAKING CHANGE:
    Many dependencies that were previously exported from specific
    APIs are now exported from angular2/core. Affected exports, which
    should now be included from angular2/core include:

    angular2/forms
    angular2/di
    angular2/directives
    angular2/change_detection
    angular2/bootstrap (except for dart users)
    angular2/render
    angular2/metadata
    angular2/debug
    angular2/pipes
Closes #3977

modules/angular2/http.ts

@@ -4,7 +4,7 @@
  * The http module provides services to perform http requests. To get started, see the {@link Http}
  * class.
  */
-import {bind, Binding} from 'angular2/di';
+import {bind, Binding} from 'angular2/core';
 import {Http, Jsonp} from './src/http/http';
 import {XHRBackend, XHRConnection} from './src/http/backends/xhr_backend';
 import {JSONPBackend, JSONPConnection} from './src/http/backends/jsonp_backend';