Insert caesium specific metadata

[the-liquid-metal]

Another hard thing to do when using caesium with other tools is resuming the workflow when other task interrupt or we forgot to do our own standard task.

It would be helpful if caesium insert it's own metadata into the file whatever it does (generating new output, skipping larger file, skipping below the threshold). If possible, create new tag. If not, concat with already exist user comment tag.

Additional option is needed below the keep metadata option: insert caesium metadata.