refactor(render): use render layer fully

Introduces angular2/src/core/compiler/ViewFactory which
extracts ProtoView.instantiate and replaces ViewPool.

Note: This is a work in progress commit to unblock other commits.
There will be follow ups to add unit tests, remove TODOs, …

modules/angular2/src/core/dom/element.js

@@ -1,16 +0,0 @@
-import {DOM} from 'angular2/src/dom/dom_adapter';
-import {normalizeBlank} from 'angular2/src/facade/lang';
-
-/**
- * @publicModule angular2/angular2
- */
-export class NgElement {
-  domElement;
-  constructor(domElement) {
-    this.domElement = domElement;
-  }
-
-  getAttribute(name:string) {
-    return normalizeBlank(DOM.getAttribute(this.domElement, name));
-  }
-}