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/upgrade/src/metadata.ts

@@ -7,7 +7,7 @@
  */
 
 import {DirectiveResolver} from '@angular/compiler';
-import {DirectiveMetadata, Type} from '@angular/core';
+import {Directive, Type} from '@angular/core';
 
 var COMPONENT_SELECTOR = /^[\w|-]*$/;
 var SKEWER_CASE = /-(\w)/g;
@@ -32,7 +32,7 @@ export interface ComponentInfo {
 }
 
 export function getComponentInfo(type: Type<any>): ComponentInfo {
-  var resolvedMetadata: DirectiveMetadata = directiveResolver.resolve(type);
+  var resolvedMetadata: Directive = directiveResolver.resolve(type);
   var selector = resolvedMetadata.selector;
   if (!selector.match(COMPONENT_SELECTOR)) {
     throw new Error('Only selectors matching element names are supported, got: ' + selector);