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/benchmarks/src/naive_infinite_scroll/app.ts

@@ -2,7 +2,7 @@ import {isPresent} from 'angular2/src/core/facade/lang';
 import {getIntParameter, bindAction} from 'angular2/src/test_lib/benchmark_util';
 import {TimerWrapper} from 'angular2/src/core/facade/async';
 import {ScrollAreaComponent} from './scroll_area';
-import {NgIf, NgFor} from 'angular2/directives';
+import {NgIf, NgFor} from 'angular2/core';
 import {DOM} from 'angular2/src/core/dom/dom_adapter';
 import {document} from 'angular2/src/core/facade/browser';
 

modules/benchmarks/src/naive_infinite_scroll/cells.ts

@@ -1,6 +1,6 @@
 import {ListWrapper, Map} from 'angular2/src/core/facade/collection';
 import {Company, Opportunity, Offering, Account, CustomDate, STATUS_LIST} from './common';
-import {NgFor} from 'angular2/directives';
+import {NgFor} from 'angular2/core';
 
 import {Component, Directive, View} from 'angular2/angular2';
 

modules/benchmarks/src/naive_infinite_scroll/index.ts

@@ -3,7 +3,7 @@ import {bootstrap} from 'angular2/bootstrap';
 import {App} from './app';
 
 import {APP_VIEW_POOL_CAPACITY} from 'angular2/src/core/compiler/view_pool';
-import {bind} from 'angular2/di';
+import {bind} from 'angular2/core';
 
 export function main() {
   bootstrap(App, createBindings());

modules/benchmarks/src/naive_infinite_scroll/scroll_area.ts

@@ -14,7 +14,7 @@ import {
 } from './common';
 import {generateOfferings} from './random_data';
 import {ScrollItemComponent} from './scroll_item';
-import {NgFor} from 'angular2/directives';
+import {NgFor} from 'angular2/core';
 
 @Component({
   selector: 'scroll-area',