Implement family-level pages showing aggregated graphs

Currently atlas is about single relays, many operators run more than a single relay and would like to see the aggregated data of all their relays on a single page with the graphs showing all relays in stacked way. This allows them to see how they are doing across all their relays.

example graphs: https://nos-oignons.net/Services/index.en.html

To avoid discussing how to identify MyFamilies lets just use onionoo lookup: https://atlas.torproject.org/#search/family:

This would also create an incentive for properly configuring MyFamily since incorrect set MyFamily would result

relay operators find this useful (counted ~11) https://lists.torproject.org/pipermail/tor-relays/2017-September/012942.html https://twitter.com/nusenu_/status/907366138149044224