xAOD file metadata style
This enforces a style similar to what I picked up from @akraszna's work on EventFormatCnv on all the FileMetaData sources. With these style changes in the functional changes required to make FileMetaData MT-friendly will can be cleanly submitted in a later request.
Note that in the job options snipped I linked the default test AOD. In that way it can just be picked up and used to test the FileMetaData.