0.2.0: Controller should gracefully handle node deletion coinciding with a WATCH stream reset

[cbgbt]

Issue or Feature Request:

The controller uses into_iter_touched(), which can miss deletion events under certain circumstances (see the linked docs).

We need to periodically refresh the entire Store object in the controller in case deletion events are missed.

[cbgbt]

Rather than into_iter_touched(), we actually use try_flatten_touched(), which uses into_iter_touched().