feat(ng-repeat): initial implementaion of ng-repeat.

- adds support for content bindings via '[]'.
- directives module

modules/facade/src/dom.dart

@@ -53,6 +53,9 @@ class DOM {
   static insertAfter(el, node) {
     el.parentNode.insertBefore(node, el.nextNode);
   }
+  static getText(Element el) {
+    return el.text;
+  }
   static setText(Text text, String value) {
     text.text = value;
   }

modules/facade/src/dom.es6

@@ -49,6 +49,9 @@ export class DOM {
   static setInnerHTML(el, value) {
     el.innerHTML = value;
   }
+  static getText(el: Element) {
+    return el.textContent;
+  }
   static setText(text:Text, value:string) {
     text.nodeValue = value;
   }