fixed: Auto flags didn't work for items without a VideoInfoTag
changed: Only update infotag when we got streamdetails else we'll may create an empty one
changed: Only try to get streamdetails when we have no infotag or no streamdetails already
changed: Use IsVideo(true) to determine whether it's a real video file
fixed: Setting streamdetails for auto thumbs/flags didn't work for items with incomplete/empty infotags
changed: Improve logic in GetStreamDetails()