show_file displays associated records:
input_records = records where file is used as input
output_recod = record from which file was generated
Possible issues/further notes:
- expecting len(output_record) == 1. Necessary to verify?
- passing input_records, output_record in all mimetype cases except
when no content is found. For now only tested data type text/pascal.
- could also adjust templates show_csv and show_image...