Language codes in subtitle name

[drzazga3009]

I think this is very important feature. QNapi should add language code to the subtitle file name (Polish or English, QNapi knows the language of downloaded subtitles so it shouldn't be a big deal. Also there should be an option do download subtitles in 2 languages.

[uded]

I think this is similar, in a subject and general substance, to #72