feat(directives): export collection of core directives

Closes #1524

modules/angular2/directives.js

@@ -2,11 +2,61 @@
  * @module
  * @public
  * @description
- * Common directives shipped with Angualr.
+ * Common directives shipped with Angular.
  */
 
+import {CONST_EXPR} from './src/facade/lang';
+import {For} from './src/directives/for';
+import {If} from './src/directives/if';
+import {NonBindable} from './src/directives/non_bindable';
+import {Switch, SwitchWhen, SwitchDefault} from './src/directives/switch';
+
 export * from './src/directives/class';
 export * from './src/directives/for';
 export * from './src/directives/if';
 export * from './src/directives/non_bindable';
 export * from './src/directives/switch';
+
+/**
+ * A collection of the Angular core directives that are likely to be used in each and every Angular application.
+ *
+ * This collection can be used to quickly enumerate all the built-in directives in the `@View` annotation. For example,
+ * instead of writing:
+ *
+ * ```
+ * import {If, For, Switch, SwitchWhen, SwitchDefault} from 'angular2/angular2';
+ * import {OtherDirective} from 'myDirectives';
+ *
+ * @Component({
+ *  selector: 'my-component'
+ * })
+ * @View({
+ *   templateUrl: 'myComponent.html',
+ *   directives: [If, For, Switch, SwitchWhen, SwitchDefault, OtherDirective]
+ * })
+ * export class MyComponent {
+ *   ...
+ * }
+ * ```
+ * one could enumerate all the core directives at once:
+ *
+ ** ```
+ * import {coreDirectives} from 'angular2/angular2';
+ * import {OtherDirective} from 'myDirectives';
+ *
+ * @Component({
+ *  selector: 'my-component'
+ * })
+ * @View({
+ *   templateUrl: 'myComponent.html',
+ *   directives: [coreDirectives, OtherDirective]
+ * })
+ * export class MyComponent {
+ *   ...
+ * }
+ * ```
+ *
+ */
+export const coreDirectives:List = CONST_EXPR([
+  For, If, NonBindable, Switch, SwitchWhen, SwitchDefault
+]);