Consider using DROID library for format detection
Given that PRONOM codes are going to be used to specify file format, and the PRONOM project provide the DROID library and a signature file to detect all PRONOM formats, we should consider using the DROID library internally in Nikita to detect formats.
Information about DROID is available from http://digital-preservation.github.io/droid/, and information about PRONOM and the DROID signature file provided is available from http://www.nationalarchives.gov.uk/PRONOM/.
The current code detecting formats is in DocumentObjectService.java.