(relays|bridges)_published in Pyonionoo should not depend on relays/bridges contained in result
Right now, (relays|bridges)_published
in Pyonionoo contains the latest timestamp of relays/bridges contained in the result. If there are no bridges/relays, the respective published time is 1900-01-01. If the returned bridges/relays were not offline for a few hours, that time is returned as published time.
I admit that the Onionoo protocol specification was imprecise there by specifying what's currently implemented in Pyonionoo. But the current Onionoo behavior makes more sense for clients. Tweaked the specification.
The (relays|bridges)_published
fields should contain the timestamps when the last consensus known to Onionoo/Pyonionoo became valid and when the last known bridge network status was published.