Now an alert tracks files that have recently been added. As a large file
is added, it will have its own alert, that then combines with the tracker
when dones.
Also used for combining sanity checker alerts, as it could possibly want to
display a lot.
Added knownRemotes to DaemonStatus. This list is not entirely trivial to
calculate, and having it here should make it easier to add/remove remotes
on the fly later on. It did require plumbing the daemonstatus through to
some more threads.
