chore(ts): duplicate the .es6 files in the facade directory to TypeScript.

Adds a gulp task which builds the .ts files (in the cjs build only).
The new files have extension .ts since they are now valid typescript.
Unfortunately until Typescript can emit System.require, we have to keep the old .es6 version
so traceur works inside the Karma preprocessor. This should be fixed soon.

modules/angular2/src/core/compiler/pipeline/compile_element.js

@@ -76,7 +76,7 @@ export class CompileElement {
     this.ignoreBindings = false;
     this.contentTagSelector = null;
     // description is calculated here as compilation steps may change the element
-    var tplDesc = assertionsEnabled()? getElementDescription(element) : null;
+    var tplDesc = getElementDescription(element);
     if (compilationUnit !== '') {
       this.elementDescription = compilationUnit;
       if (isPresent(tplDesc)) this.elementDescription += ": " + tplDesc;