feat(forms): add optional controls

modules/angular2/src/forms/validators.js

@@ -4,7 +4,7 @@ import {List, ListWrapper, StringMapWrapper} from 'angular2/src/facade/collectio
 import {ControlGroup, Control} from 'angular2/forms';
 
 export function required(c:Control) {
-  return isBlank(c.value) || c.value === "" ? {"required" : true} : null;
+  return isBlank(c.value) || c.value == "" ? {"required" : true} : null;
 }
 
 export function nullValidator(c:Control) {
@@ -13,17 +13,18 @@ export function nullValidator(c:Control) {
 
 export function compose(validators:List<Function>):Function {
   return function(c:Control) {
-    return ListWrapper.reduce(validators, (res, validator) => {
+    var res = ListWrapper.reduce(validators, (res, validator) => {
       var errors = validator(c);
       return isPresent(errors) ? StringMapWrapper.merge(res, errors) : res;
     }, {});
+    return StringMapWrapper.isEmpty(res) ? null : res;
   }
 }
 
 export function controlGroupValidator(c:ControlGroup) {
   var res = {};
   StringMapWrapper.forEach(c.controls, (control, name) => {
-    if (isPresent(control.errors)) {
+    if (control.active && isPresent(control.errors)) {
       res[name] = control.errors;
     }
   });