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/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';
 
 /**