Write script to aggregate relay weights by country, AS, or relay family

lunar is interested in adding pie charts about relays/capacity per AS network and similar statistics to Atlas. In order to do this, Onionoo should provide these data in a convenient way. These data would be based on the very last consensus and would not incorporate any history.

We should probably wait for the Python Onionoo to implement this and not extend the Java Onionoo. Setting priority to minor.