Make order of sorted results deterministic

A non-deterministic element in Onionoo docs is the order of entries. When there is a tie in the used order parameter order is arbitrary and will differ. A simple solution could be to always sort by fingerprint in case of a tie.

See this patch.

Open steps:

• rebase to master,
• add a change log entry, and
• provide a metrics-web patch for updating the ​specification