feat(i18n): add ngPlural directive

modules/angular2/test/public_api_spec.ts

@@ -381,6 +381,7 @@ var NG_COMMON = [
   'NgFormModel.value',
   'NgIf',
   'NgIf.ngIf=',
+  'NgLocalization',
   'NgModel',
   'NgModel.asyncValidator',
   'NgModel.control',
@@ -405,6 +406,14 @@ var NG_COMMON = [
   'NgModel.viewModel',
   'NgModel.viewModel=',
   'NgModel.viewToModelUpdate()',
+  'NgPlural',
+  'NgPlural.cases',
+  'NgPlural.cases=',
+  'NgPlural.ngAfterContentInit()',
+  'NgPlural.ngPlural=',
+  'NgPluralCase',
+  'NgPluralCase.value',
+  'NgPluralCase.value=',
   'NgSelectOption',
   'NgStyle',
   'NgStyle.ngDoCheck()',