Mantis #4425 : Try to lowest Picture Generation Thread and use ThreadPool to be less aggressive.
Enable WMV WMA codec format setting for LAV suite (setting will be change only on first run and if lav is set as default splitter)
Merge remote-tracking branch 'remotes/origin/BUG-4425-Picture_Thumbnail_Generation_can_be_too_agressive'
Merge remote-tracking branch 'remotes/origin/BUG-4429-Default_LAV_Setting_can't_play_WMV_WMA_files'