Remember managed files


There should be some persistent state storage for every serial with informations about renaming operations, so it can be reverted in some cases or just search for original file name (when looking for subtitles for one release). Then it can also remember some ignore flag for files, which should stay out of system.
Main problem is with identification of file. It cannot be obviously from filename, when it's changed. However partly it can be based on byte length of file. But there must be also some control checksum of file to be sure and it must be really quick for video files. For subtitles and other small files can be used standard crc32.