cleanup(core): stop reexporting angular2/common from angular2/core

All common directives, forms, and pipes have been moved out of angular2/core,
but we kept reexporting them to make transition easier.

This commit removes the reexports.

BREAKING CHANGE

Before

import {NgIf} from 'angular2/core';

After

import {NgIf} from 'angular2/common';

Closes #5362

modules/playground/src/async/index.ts

@@ -1,5 +1,6 @@
 import {bootstrap} from 'angular2/bootstrap';
-import {NgIf, Component, View} from 'angular2/core';
+import {Component, View} from 'angular2/core';
+import {NgIf} from 'angular2/common';
 import {TimerWrapper} from 'angular2/src/facade/async';
 
 @Component({selector: 'async-app'})

modules/playground/src/material/button/index.ts

@@ -1,5 +1,6 @@
 import {bootstrap} from 'angular2/bootstrap';
-import {bind, provide, Component, NgFor, View, ViewEncapsulation} from 'angular2/core';
+import {bind, provide, Component, View, ViewEncapsulation} from 'angular2/core';
+import {NgFor} from 'angular2/common';
 import {UrlResolver} from 'angular2/compiler';
 import {MdButton, MdAnchor} from 'angular2_material/src/components/button/button';
 import {commonDemoSetup, DemoUrlResolver} from '../demo_common';

modules/playground/src/model_driven_forms/index.ts

@@ -7,12 +7,9 @@ import {
   NgFormModel,
   FormBuilder,
   NgIf,
-  NgFor,
-  Component,
-  Directive,
-  View,
-  Host
-} from 'angular2/core';
+  NgFor
+} from 'angular2/common';
+import {Component, Directive, View, Host} from 'angular2/core';
 
 import {RegExpWrapper, print, isPresent} from 'angular2/src/facade/lang';
 

modules/playground/src/observable_models/app.dart

@@ -3,7 +3,7 @@ library benchmarks.src.naive_infinite_scroll.app;
 import "package:angular2/src/facade/collection.dart" show List, ListWrapper;
 import "scroll_area.dart" show ScrollAreaComponent;
 import "package:angular2/angular2.dart" show Component, Directive, View, IterableDiffers, SkipSelf, Binding;
-import "package:angular2/core.dart" show ObservableListDiffFactory, NgIf, NgFor;
+import "package:angular2/common.dart" show ObservableListDiffFactory, NgIf, NgFor;
 import 'package:observe/observe.dart' show ObservableList;
 
 createDiffers(IterableDiffers parent) {

modules/playground/src/observable_models/cells.dart

@@ -4,7 +4,7 @@ import "package:angular2/src/facade/collection.dart"
     show List, ListWrapper, Map;
 import "common.dart"
     show Company, Opportunity, Offering, Account, CustomDate, STATUS_LIST;
-import "package:angular2/core.dart" show NgFor;
+import "package:angular2/common.dart" show NgFor;
 import "package:angular2/angular2.dart" show Component, Directive, View, ChangeDetectionStrategy;
 
 class HasStyle {

modules/playground/src/observable_models/scroll_area.dart

@@ -14,7 +14,7 @@ import "common.dart"
         HEIGHT;
 import "random_data.dart" show generateOfferings;
 import "scroll_item.dart" show ScrollItemComponent;
-import "package:angular2/core.dart" show NgFor;
+import "package:angular2/common.dart" show NgFor;
 
 @Component(selector: "scroll-area", changeDetection: ChangeDetectionStrategy.OnPushObserve)
 @View(directives: const [ScrollItemComponent, NgFor], template: '''

modules/playground/src/order_management/index.ts

@@ -1,18 +1,16 @@
 import {bootstrap} from 'angular2/bootstrap';
 import {
-  NgIf,
-  NgFor,
   Component,
   Directive,
   Host,
   forwardRef,
   Provider,
   EventEmitter,
-  FORM_DIRECTIVES,
   Injectable,
   Input,
   Output
 } from 'angular2/core';
+import {NgIf, NgFor, FORM_DIRECTIVES} from 'angular2/common';
 
 import {ListWrapper} from 'angular2/src/facade/collection';
 

modules/playground/src/person_management/index.ts

@@ -1,16 +1,6 @@
 import {bootstrap} from 'angular2/bootstrap';
-import {
-  NgIf,
-  NgFor,
-  Component,
-  Directive,
-  View,
-  Host,
-  forwardRef,
-  Provider,
-  FORM_DIRECTIVES,
-  Injectable
-} from 'angular2/core';
+import {Component, Directive, View, Host, forwardRef, Provider, Injectable} from 'angular2/core';
+import {NgIf, NgFor, FORM_DIRECTIVES} from 'angular2/common';
 
 import {CONST_EXPR} from 'angular2/src/facade/lang';
 

modules/playground/src/template_driven_forms/index.ts

@@ -1,20 +1,15 @@
 import {bootstrap} from 'angular2/bootstrap';
+import {Component, Directive, View, Host, forwardRef, Provider} from 'angular2/core';
 import {
   ControlGroup,
   NgIf,
   NgFor,
-  Component,
-  Directive,
-  View,
-  Host,
   NG_VALIDATORS,
-  forwardRef,
-  Provider,
   FORM_DIRECTIVES,
   NgControl,
   Validators,
   NgForm
-} from 'angular2/core';
+} from 'angular2/common';
 
 import {RegExpWrapper, print, isPresent, CONST_EXPR} from 'angular2/src/facade/lang';
 

modules/playground/src/todo/index.ts

@@ -1,5 +1,6 @@
 import {bootstrap} from 'angular2/bootstrap';
-import {NgFor, Component, View} from 'angular2/core';
+import {Component, View} from 'angular2/core';
+import {NgFor} from 'angular2/common';
 import {Store, Todo, TodoFactory} from './services/TodoStore';
 
 @Component({selector: 'todo-app', viewProviders: [Store, TodoFactory]})