refactor: rename annotations to metadata

BREAKING CHANGE (maybe)

Well as long as our customers use public API this should not be a
breaking change, but we have changed import structure as well as
internal names, so it could be breaking.

import:
  angular2/annotations => angular2/metadata

Classes:
  *Annotations => *Metadata
  renderer.DirectiveMetadata => renderer.RendererDirectiveMetadata
  renderer.ElementBinder => renderer.RendererElementBinder
  impl.Directive => impl.DirectiveMetadata
  impl.Component => impl.ComponentMetadata
  impl.View => impl.ViewMetadata

Closes #3660

modules/angular2/test/core/metadata/decorators_spec.dart

@@ -0,0 +1,5 @@
+library angular2.test.core.annotations.decorators_dart_spec;
+
+main() {
+  // not relavant for dart.
+}

modules/angular2/test/core/metadata/decorators_spec.ts

@@ -0,0 +1,36 @@
+import {
+  AsyncTestCompleter,
+  beforeEach,
+  ddescribe,
+  describe,
+  expect,
+  iit,
+  inject,
+  it,
+  xit,
+} from 'angular2/test_lib';
+
+import {Component, View, Directive} from 'angular2/angular2';
+import {reflector} from 'angular2/src/reflection/reflection';
+
+export function main() {
+  describe('es5 decorators', () => {
+    it('should declare directive class', () => {
+      var MyDirective = Directive({}).Class({constructor: function() { this.works = true; }});
+      expect(new MyDirective().works).toEqual(true);
+    });
+
+    it('should declare Component class', () => {
+      var MyComponent =
+          Component({}).View({}).View({}).Class({constructor: function() { this.works = true; }});
+      expect(new MyComponent().works).toEqual(true);
+    });
+
+    it('should create type in ES5', () => {
+      function MyComponent(){};
+      var as;
+      (<any>MyComponent).annotations = as = Component({}).View({});
+      expect(reflector.annotations(MyComponent)).toEqual(as.annotations);
+    });
+  });
+}