Improved auto search handling

[bbviking]

Changes:

• Auto search uses the existing 'parse_language' function to parse the 'preferredlang' value to allow for proper handling of 'Original' and 'Forced Only' subtitle languages
• If Kodi's subtitle language is set to 'Forced Only' then auto search will now treat it as if 'Prefer Forced' is set in a4ksubtitles
• If Kodi's subtitle language is set to 'None' will no longer attempt auto select
• If Kodi's language is not 'Forced Only' will now attempt to pick a subtitle that isn't forced, even if the embedded forced subtitles are marked as default
• If the subtitle being set is the same as the currently enabled subtitles then it will no longer set it to prevent subtitle delay from switching