Use file_type within identification logic (50 cow points)

[brifordwylie]

Right now we just look at mime_type and then punt to extension, put file_type logic when identifying unknown files.

[brifordwylie]

Actually the use case here was for files that were marked as application/octet, which is just the general term for 'data'. So in this case the file info doesn't actually give us any additional information. I did so a small reorg of logic. So closing this.