Sub title selection should be done according to the language selection

[kelson42]

If I choose "French" in the language selection, automatically the subtitle in French should be chosen. Exception is English (because the soundtrack is in English).

[benoit74]

Video soundtrack is not necessarily in English, there is few videos in other languages. We need to take this into account.

So the idea is more: whenever a language has been selected in the combobox and stored appropriately thanks to solution implemented in #208, we should automatically activate the matching subtitle in the video player if the video audio is not the selected language and language is available.