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/src/core/change_detection/change_detection.ts

@@ -11,7 +11,7 @@ import {
   ChangeDetectorDefinition,
   ChangeDetectorGenConfig
 } from './interfaces';
-import {Injector, Inject, Injectable, OpaqueToken, Optional, Binding} from 'angular2/di';
+import {Injector, Inject, Injectable, OpaqueToken, Optional, Binding} from 'angular2/src/core/di';
 import {StringMap, StringMapWrapper} from 'angular2/src/core/facade/collection';
 import {
   CONST,

modules/angular2/src/core/change_detection/differs/iterable_differs.ts

@@ -1,7 +1,7 @@
 import {isBlank, isPresent, BaseException, CONST} from 'angular2/src/core/facade/lang';
 import {ListWrapper} from 'angular2/src/core/facade/collection';
 import {ChangeDetectorRef} from '../change_detector_ref';
-import {Binding, SkipSelfMetadata, OptionalMetadata, Injectable} from 'angular2/di';
+import {Binding, SkipSelfMetadata, OptionalMetadata, Injectable} from 'angular2/src/core/di';
 
 export interface IterableDiffer {
   diff(object: Object): any;

modules/angular2/src/core/change_detection/differs/keyvalue_differs.ts

@@ -1,7 +1,7 @@
 import {isBlank, isPresent, BaseException, CONST} from 'angular2/src/core/facade/lang';
 import {ListWrapper} from 'angular2/src/core/facade/collection';
 import {ChangeDetectorRef} from '../change_detector_ref';
-import {Binding, SkipSelfMetadata, OptionalMetadata, Injectable} from 'angular2/di';
+import {Binding, SkipSelfMetadata, OptionalMetadata, Injectable} from 'angular2/src/core/di';
 
 export interface KeyValueDiffer {
   diff(object: Object);

modules/angular2/src/core/change_detection/observable_facade.dart

@@ -1,3 +1,5 @@
+library change_detection.observable_facade;
+
 import 'package:observe/observe.dart';
 
 bool isObservable(value) => value is Observable;