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/test/transform/integration/all_tests.dart

@@ -44,8 +44,8 @@ void allTests() {
     'angular2|lib/src/reflection/reflection_capabilities.dart':
         '../common/reflection_capabilities.dart',
     'angular2|lib/di.dart': '../../../lib/di.dart',
-    'angular2|lib/src/di/annotations.dart':
-        '../../../lib/src/di/annotations.dart',
+    'angular2|lib/src/di/annotations_impl.dart':
+        '../../../lib/src/di/annotations_impl.dart',
   };
 
   var tests = [