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-cli/test/static_reflector_spec.ts

@@ -7,7 +7,7 @@
  */
 
 import {StaticReflector, StaticReflectorHost, StaticSymbol} from '@angular/compiler-cli/src/static_reflector';
-import {HostListenerMetadata, animate, group, keyframes, sequence, state, style, transition, trigger} from '@angular/core';
+import {HostListener, animate, group, keyframes, sequence, state, style, transition, trigger} from '@angular/core';
 import {ListWrapper} from '@angular/facade/src/collection';
 import {isBlank} from '@angular/facade/src/lang';
 import {MetadataCollector} from '@angular/tsc-wrapped';
@@ -92,7 +92,7 @@ describe('StaticReflector', () => {
         host.findDeclaration('src/app/hero-detail.component', 'HeroDetailComponent');
     let props = reflector.propMetadata(HeroDetailComponent);
     expect(props['hero']).toBeTruthy();
-    expect(props['onMouseOver']).toEqual([new HostListenerMetadata('mouseover', ['$event'])]);
+    expect(props['onMouseOver']).toEqual([new HostListener('mouseover', ['$event'])]);
   });
 
   it('should get an empty object from propMetadata for an unknown class', () => {