Live view 2nd edition

[y-lohse]

If a snapshot is added from outside the current page (eg. another tab or the bookmarklet), the list won't be up to date. We should run a check every couple of seconds to re-fetch the list (but only when the page has focus) and if any snapshots are unprocessed, we need to watch them.

The 2 mecanics need to be somewhat combined to avoid excessive server requests.