Add additional trackers per torrent

Torrents can be uniquely identified by a hash. It would be good to be able to search multiple site for torrents by hash. Adding a torrent already added to your torrent client generally causes the torrent client to consolidate the list of trackers. This makes the torrent faster.

This could be done by creating a `TorrentProvider` class with a `getByHash` function used to attain torrents by their hash. This may then return a `Torrent` object that could be added to the `TorrentClient`.