Revision 7036685968a4ab4a8cda138688c8ec6a8ea5e84c

Refactored ContentView value object

A common eZ\Publish\Core\MVC\Symfony\View interface is added.
Each View gets its own concrete object, inheriting from an abstract BaseView.

Additional interfaces exist for value objects contained within the view:
LocationValueView, ContentValueView, BlockValueView. They expose getters
that give access to those objects.

Ex: ContentView contains both a Content and a Value.
It implements View, LocationValueView and ContentValueView.