Correct the name of the item in the comment.
Implement the visitedShareRoomsCollection with a custom sync() method, so
we can preserve the collection to local storage.

Currently, using a bogus item to exercise the functionality.

And currently, it works only partly.  The model is established, but isn't
correctly realized.  I've run out of time for the day, and will work on
that next.
Start to implement loadVisitedShareRooms similarly to the loadMyShareRooms,
but using the visitedShareRoomsCollection, which is responsible for the
storage/sync.

There still is a detail handled in the views that is probably the
responsibility of the collections, the url for the top-level models.  That
needs to be fixed, as does the visited ShareRooms model, in general.