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/examples/src/model_driven_forms/index.ts

@@ -1,5 +1,17 @@
-import {bootstrap, NgIf, NgFor, Component, Directive, View, Host} from 'angular2/bootstrap';
-import {FORM_DIRECTIVES, NgControl, Validators, NgFormModel, FormBuilder} from 'angular2/forms';
+import {bootstrap} from 'angular2/bootstrap';
+import {
+  FORM_DIRECTIVES,
+  NgControl,
+  Validators,
+  NgFormModel,
+  FormBuilder,
+  NgIf,
+  NgFor,
+  Component,
+  Directive,
+  View,
+  Host
+} from 'angular2/core';
 
 import {RegExpWrapper, print, isPresent} from 'angular2/src/core/facade/lang';