Remove config option: remove_peerless_torrents?

[josecelano]

Relates to: #566

There is a config option called remove_peerless_torrents:

remove_peerless_torrents = true

By default is true. When tru removes torrents from the tracker with no peers.

• Does it make sense to disable it?
• Why do you want to keep torrents with empty peer lists?

I think there could be a couple of reasons to keep those torrents:

1. It would be faster to add peers again if the torrent entry already exists in the torrent repository.
2. Users would like to have stats for all the torrents that have ever been announced.

For the second reason, we already have persistent torrent stats. We could add a new feature to persist torrents even if you do not want to persist stats. It could be a new table only with the torrent infohash. I think this option would be better than growing objects in memory forever.

cc @da2ce7