Makes writeinfojson behaving exactly as writethumbnail in case where filename contains mediafile extension.
Case:
video.mp4 converted to music.mp3 would yield music.mp4.info.json instead music.mp3.info.json or music.info.json
The report_progress function will accept eta and percent with None value and will set the message to 'Unknow ETA' or 'Unknown %'.
Otherwise the values must be numbers.