Error in merge request !76

detectors_file cannot be specified using the -o command anymore. If used, Corryvreckan complains that no detectors_file was declared.

2018-12-17 17:07 williamm@pclcd23:corryvreckan-tests$ ./configs/analyse_cp2.sh 29876
|17:07:46.587|  (STATUS) Welcome to Corryvreckan v0.9.2
|17:07:46.588|   (FATAL) Error in the configuration file:
                          Key 'detectors_file' in global section does not exist
                         The configuration file needs to be updated! Cannot continue...

I assume this is an error in !76 (merged) that we missed.