Update to air traffic controller training guidance (CAP 584)

CAP 584 has been amended to update the reference for the Air Traffic Controllers – Licensing CAP which has changed from CAP 744 to CAP 1251. The initial training terminal objectives for ratings have been moved to the CAP 794. This update also reflects the post transition period of Commission Regulation (EU) 2015/340: the introduction of best practice for the conduct of written examinations.