feat(core): add ability to reflect DOM properties as attributes

By binding the token `DOM_REFLECT_PROPERTIES_AS_ATTRIBUTES` provided by 
the dom_renderer module to `true` in the root injector (i.e. bootstrap()), 
all elements whose properties are set by angular will be reflected as 
attributes with the prefix "ng-reflect-".

Fixes #2910

modules/angular2/angular2.ts

@@ -64,4 +64,8 @@ export {
   RenderViewRef,
   RenderProtoViewRef
 } from 'angular2/src/render/api';
-export {DomRenderer, DOCUMENT_TOKEN} from 'angular2/src/render/dom/dom_renderer';
+export {
+  DomRenderer,
+  DOCUMENT_TOKEN,
+  DOM_REFLECT_PROPERTIES_AS_ATTRIBUTES
+} from 'angular2/src/render/dom/dom_renderer';