Document database process

[erinhmclark]

Document the significance of what gets stored in the database output.

"no archiver" vs "nothing archived" message.
Metadata sets it to 'no archiver' on initialisation, but if nothing is extracted it gets set to 'nothin archived' in the orchestration process

        if result.is_empty():
            result.status = "nothing archived"

I think the distinction here is if there is an enricher, e.g. screenshot, which is independent of the extraction the row is stored this is stored as 'no archiver', but if there's no extractor and no media is stored then is set to 'nothing archived'