Fix online followers counter

[miguelfreitas]

Current online followers counter is completely wrong.

I've tried using m_policy.num_peers() [aka torrent_status::list_peers] but it doesn't work. This number may get really big with all peers that have been known at some point so it is completely unreliable for this application.

A better estimation is needed.

note: torrent::dht_announce() is where the value is passed to m_ses.m_dht->announce.

[homlett]

To fix that, I propose to change the paradigm... I explain myself : I'm not sure the followers counter is the most pertinent value. On twitter, we know that someone can have a lot of followers but not a lot of readers or active followers. It's not a very good indicator.

So maybe we can try to do better and to implement a kind of influence indicator (like Klout). It could be a skilful calculation based on peers number, peers activity, twists number, retwists number, last twist date, etc. This could be updated every 24 hours for example.

I don't know twister very well, so there are probably a better way to do that, but it's just a proposition to think together.

What do you think?