Improved detection of DVDs playing in MovingPictures.

Note: there is still an issue with scrobble as MovingPictures doesn't send us a watched event, we may need to to workaround this in the meantime.
Fixed a possible race condition which caused a crash when switching windows with/without a dashboard.

Fixed the crash, will need to pass the windowid as a parameter to the timer that updates the dashboard rather than evaluate it whilst in the methods populating the data as it can potentially change if switching windows very fast.