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/angular2/test/common/forms/directives_spec.ts

@@ -17,6 +17,8 @@ import {
 
 import {SpyNgControl, SpyValueAccessor} from '../spies';
 
+import {QueryList} from 'angular2/core';
+
 import {
   ControlGroup,
   Control,
@@ -32,9 +34,8 @@ import {
   DefaultValueAccessor,
   CheckboxControlValueAccessor,
   SelectControlValueAccessor,
-  QueryList,
   Validator
-} from 'angular2/core';
+} from 'angular2/common';
 
 
 import {selectValueAccessor, composeValidators} from 'angular2/src/common/forms/directives/shared';

modules/angular2/test/common/forms/form_builder_spec.ts

@@ -9,7 +9,7 @@ import {
   afterEach,
   el
 } from 'angular2/testing_internal';
-import {Control, FormBuilder} from 'angular2/core';
+import {Control, FormBuilder} from 'angular2/common';
 import {PromiseWrapper} from 'angular2/src/facade/promise';
 
 export function main() {

modules/angular2/test/common/forms/integration_spec.ts

@@ -19,23 +19,21 @@ import {
 } from 'angular2/testing_internal';
 
 import {DOM} from 'angular2/src/core/dom/dom_adapter';
+import {Input, Provider, forwardRef} from 'angular2/core';
 import {
-  Input,
   Control,
   ControlGroup,
   ControlValueAccessor,
   FORM_DIRECTIVES,
   NG_VALIDATORS,
   NG_ASYNC_VALIDATORS,
-  Provider,
   NgControl,
   NgIf,
   NgFor,
   NgForm,
   Validators,
-  forwardRef,
   Validator
-} from 'angular2/core';
+} from 'angular2/common';
 import {By} from 'angular2/platform/browser';
 import {ListWrapper} from 'angular2/src/facade/collection';
 import {ObservableWrapper} from 'angular2/src/facade/async';

modules/angular2/test/common/forms/model_spec.ts

@@ -13,7 +13,7 @@ import {
   tick,
   inject
 } from 'angular2/testing_internal';
-import {ControlGroup, Control, ControlArray, Validators} from 'angular2/core';
+import {ControlGroup, Control, ControlArray, Validators} from 'angular2/common';
 import {IS_DART, isPresent, CONST_EXPR} from 'angular2/src/facade/lang';
 import {PromiseWrapper} from 'angular2/src/facade/promise';
 import {TimerWrapper, ObservableWrapper, EventEmitter} from 'angular2/src/facade/async';

modules/angular2/test/common/forms/validators_spec.ts

@@ -11,7 +11,7 @@ import {
   tick,
   el
 } from 'angular2/testing_internal';
-import {ControlGroup, Control, Validators, AbstractControl, ControlArray} from 'angular2/core';
+import {ControlGroup, Control, Validators, AbstractControl, ControlArray} from 'angular2/common';
 import {PromiseWrapper} from 'angular2/src/facade/promise';
 import {EventEmitter, ObservableWrapper, TimerWrapper} from 'angular2/src/facade/async';
 import {CONST_EXPR} from 'angular2/src/facade/lang';