After the latest gvfs gyrations, we now launch gthumb when a camera is plugged
in, but it just points at the top-level directory, leaving it to the user to
navigate down to DCIM/<whatever your camera> to find the photos, and there is no
good way to import them.

This is a pretty visible regression compared to F8, so we should look at the
unmount-wrapper approach again, now that the gvfs problems with it are solved.