Start community heartbeat support

Created by: SunilMohanAdapa

Boxes should be able to ping other boxes for health information about their mutual connections and other data. Boxes could run tests on other boxes to make sure they're still in one piece and send out communal alerts when a box is found to be failing ("Alice has a bad network connection," "Bob's sending out malware!").

Perhaps start with distributing /etc backups, key(ring) backups, or time syncing.

Might be broken out into a separate heartbeat project.