Pass contextual element directly to morph

This PR simplifies domHelpers (removes a lot of code) by reusing the same DOMHelper instance and passing contextual elements to morphs. It temporarily removes some namespacing features. There's a plan to bring them back.

/cc @mixonic
This should call `this.cloneNode(contextualElement, false);`. We will be fixing browser inconsistencies behind `this.cloneNode`.