[Fixed Position] Add element factory

Add element factory, which will take on responsibility
for populating initial states of elements and (if necessary)
prompting for user input. WTD-880.

platform/features/layout/res/templates/elements/image.html

@@ -1 +1 @@
-<img ng-src="ngModel.url" style="width: 100%; height: 100%;"></img>
+<img ng-src="{{ngModel.element.url}}" style="width: 100%; height: 100%;"></img>