add auto-download

[gonzaloUr]

No description provided.

[pogman-code]

As far as I understand the purpose of "auto" is to get the most downloaded subtitle, right?
The risk here is that you might download a file that do not match your release (different release group) and that is likely to have subs not synchronized to it.

I really like the idea to download the most downloaded one but it might be nice to check if the release group matches in addition to the completion and the amount of downloads.

And if you want to be thorough we can consider all "webrip" releases as matching one another (unlike "hdtv" releases) because they are supposed to be exactly alike (same duration, etc.)

[gonzaloUr]

Should it download no subtitles if there is any that matches the release group or download the most downloaded one although it doesn't matches?