With this commit, any component that needs an instance of the
root widget can simply require the module 'root.widget'. Based on
the context (backend, frontend, iframe), the real root.widget
will resolve to either the webclient, the website root instance, or
the iframe root instance.
This is desirable in order for the tour_manager to become a child
of the root widget, as tours are enabled in any of the above contexts.
This commit is a requirement in order to solve an issue with JS services,
in which there should be only one service provider at any given time.
Alexandre Kühn
0de5c1f076