Substitute "public" for "visited" in object names, where the name is

referring to a public share room (as opposed to a share room that is
currently being visited by the app).

I've tested manually, and noticed on my devices when trying to view, eg images, that I'm getting the "Cannot find an app to view files of this type..." error - but that happens with my ad hoc builds from the master, without these changes, as well.   Do test with a proper build, though, to make sure nothing is disrupted.

Fixes #190.