ultron: Add a small Chromium update helper.

Probably this should better be implemented in Hydra, because it's a
hack. It basically makes a sparse checkout into the home directory of
the "nixpkgsupdate" user, calls update.sh and creates a commit of the
update (largely to avoid merge conflicts).

Hydra then picks up this directory and runs its builds. Of course, there
is a chance for race conditions if the evaluator picks up the directory
while update.sh is writing sources.nix.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
mongooseim: Send startup notifications to systemd.

This is somewhat tricky in Erlang, as neither DBus nor Unix domain
sockets are available in the standard OTP library. So we add a new patch
which runs "systemd-notify" as an external program in order to inform
systemd not only about the fact that it has started but also on which
node it is running.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
chromium: Look for updates every hour.

Instead of every five minutes like before.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>