refactor(core): remove …Metadata for all decorators and use the decorator directly.

BREAKING CHANGE:
- all `…Metadata` classes have been removed. Use the corresponding decorator
  as constructor or for `instanceof` checks instead.
- Example:
  * Before: `new ComponentMetadata(…)`
  * After: `new Component(…)`
- Note: `new Component(…)` worked before as well.

modules/@angular/compiler/test/ng_module_resolver_mock_spec.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Injector, NgModule, NgModuleMetadata} from '@angular/core';
+import {Injector, NgModule} from '@angular/core';
 import {beforeEach, ddescribe, describe, expect, iit, inject, it} from '@angular/core/testing/testing_internal';
 
 import {isBlank, stringify} from '../src/facade/lang';
@@ -29,7 +29,7 @@ export function main() {
 
       it('should allow overriding the @NgModule', () => {
         ngModuleResolver.setNgModule(
-            SomeNgModule, new NgModuleMetadata({declarations: [SomeOtherDirective]}));
+            SomeNgModule, new NgModule({declarations: [SomeOtherDirective]}));
         var ngModule = ngModuleResolver.resolve(SomeNgModule);
         expect(ngModule.declarations).toEqual([SomeOtherDirective]);
       });