refactor(core): introduce ViewRef and ProtoViewRef

BREAKING CHANGES:
- `NgElement` merged into `ElementRef`
- `Compiler.compile…` returns `ProtoViewRef`
- `ViewContainer` uses `ProtoViewRef`s and `ViewRef`s.
- `ViewRef`/`ProtoViewRef` in renderer were renamed to
  `RenderViewRef`/`RenderProtoViewRef`.

Related to #1477
Closes #1592

modules/angular2/src/core/annotations/annotations.js

@@ -54,7 +54,7 @@ import {DEFAULT} from 'angular2/change_detection';
  * - `@Descendants query:Query<DirectiveType>`: A live collection of any child directives (will be implemented in later relaese).
  *
  * To inject element-specific special objects, declare the constructor parameter as:
- * - `element: NgElement` to obtain a DOM element (DEPRECATED: replacement coming)
+ * - `element: ElementRef` to obtain a reference to logical element in the view.
  * - `viewContainer: ViewContainerRef` to control child template instantiation, for {@link Viewport} directives only
  * - `bindingPropagation: BindingPropagation` to control change detection in a more granular way.
  *