feat(decorators): adds decorator versions of DI annotations.

In 'angular2/di' the symbol:
- Inject is a decorator
- InjectAnnotation is an annotation

Internally one an get a hold of annotations without *Annotations appened
(to make ts2dart work without workarounds) by importing from
'angular2/src/di/annotations_impl' instead of 'angular2/di'. This is
needed only for users that transpile through TS and through ts2dart.

modules/angular2/src/di/annotations.dart

@@ -0,0 +1,3 @@
+library angular2.di.annotations;
+
+export './annotations_impl.dart';

modules/angular2/src/di/annotations.es6

@@ -0,0 +1,13 @@
+/**
+ * This indirection is needed to free up Component, etc symbols in the public API
+ * to be used by the decorator versions of these annotations.
+ */
+
+export {
+  Inject as InjectAnnotation,
+  InjectPromise as InjectPromiseAnnotation,
+  InjectLazy as InjectLazyAnnotation,
+  Optional as OptionalAnnotation,
+  Injectable as InjectableAnnotation,
+  DependencyAnnotation,  // abstract base class, does not need a decorator
+  } from './annotations_impl';

modules/angular2/src/di/binding.js

@@ -2,7 +2,7 @@ import {Type, isBlank, isPresent, CONST} from 'angular2/src/facade/lang';
 import {List, MapWrapper, ListWrapper} from 'angular2/src/facade/collection';
 import {reflector} from 'angular2/src/reflection/reflection';
 import {Key} from './key';
-import {Inject, InjectLazy, InjectPromise, Optional, DependencyAnnotation} from './annotations';
+import {Inject, InjectLazy, InjectPromise, Optional, DependencyAnnotation} from './annotations_impl';
 import {NoAnnotationError} from './exceptions';
 
 /**

modules/angular2/src/di/decorators.dart

@@ -0,0 +1,3 @@
+library angular2.di.decorators;
+
+/* This file is empty because, Dart does not have decorators. */

modules/angular2/src/di/decorators.es6

@@ -0,0 +1,13 @@
+import {
+  InjectAnnotation,
+  InjectPromiseAnnotation,
+  InjectLazyAnnotation,
+  OptionalAnnotation,
+  InjectableAnnotation} from './annotations';
+import {makeDecorator, makeParamDecorator} from '../util/decorators';
+
+export var Inject = makeParamDecorator(InjectAnnotation);
+export var InjectPromise = makeParamDecorator(InjectPromiseAnnotation);
+export var InjectLazy = makeParamDecorator(InjectLazyAnnotation);
+export var Optional = makeParamDecorator(OptionalAnnotation);
+export var Injectable = makeDecorator(InjectableAnnotation);