Fixing detector initialisation: Although only the first proc should write the header, all procs need to create the field lists.
Fixing detector initialisation: Although only the first proc should write the header, all procs need to create the field lists.

jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,jrper/fluidity,jrper/fluidity,rjferrier/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,jrper/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,jrper/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity