Updates to torrent providers, primarily KAT search provider 

- Modified torrent metafile validation to allow metafiles starting with "d12:_info_length"
- DRYed out the TorrentProvider class's downloadResult function, which was duplicating code from the parent function, as well as never using Bricky's modified validation code in the parent's _verify_download function
- Search results are now sorted by number of seeders, so that torrents with more seeders will be prioritized (previously the order was random).
- Now discarding torrents with zero seeders.
- Added support for Alternate Scene Names to the KAT provider's search
- KAT provider's fuzzy search now works for season searches too