Rewrite subtitles downloading framework

[x] Respect language order on auto download. The process will download additional subtitles when the language found is of higher priority.
[x] Implement ignoring files containing a list of words
[x] Allow loading property page independently of MainFrame
[x] Don't start search and download automatically when auto-load subtitles is turned off.

Implement default sorting based on language selection, hearing impaired selection and internal score.

Move subtitles internal list to SubtitleDlDlg to avoid the need of synchronization.

Use native dialog box for prompt for credentials