add CUtil::GetExternalStreamNameAndLangFromFilename method to extract stream language and name from filename
[DVDPlayer] Use CUtil::GetExternalStreamDetailsFromFilename to determine external subtitles's details.
 These are language, name and flag.
dvdplayer: update current video settings when changing setting subtitles stream to be sure we keep it synced (similiar to what we already do when we show/hide subtitles)
add VideoPlayer.SubtitlesLanguage infolabel that returns full language name of current subtitles, "unknown" localized string or empty string if subtitles are disabled or video isn't playing currently
[FileInfo/Thumbs] Add language retrival from external subs while extracting thumbs.
[DVDPlayer/DVDFileInfo] Add external subs' details while updating stream details from player.