feat(forms): add ability to reset forms (#9974)

Closes #4914
Closes #4933

modules/@angular/forms/src/directives/reactive_directives/form_group_directive.ts

@@ -105,7 +105,7 @@ export const formDirectiveProvider: any =
 @Directive({
   selector: '[formGroup]',
   providers: [formDirectiveProvider],
-  host: {'(submit)': 'onSubmit()'},
+  host: {'(submit)': 'onSubmit()', '(reset)': 'onReset()'},
   exportAs: 'ngForm'
 })
 export class FormGroupDirective extends ControlContainer implements Form,
@@ -187,6 +187,8 @@ export class FormGroupDirective extends ControlContainer implements Form,
     return false;
   }
 
+  onReset(): void { this.form.reset(); }
+
   /** @internal */
   _updateDomValue() {
     this.directives.forEach(dir => {