Fix orbit packaging with last BXs of previous orbits in current orbit
Currently we have the last BXs of the previous orbit packaged in the current orbit from the firmware point of view. This causes some headaches in the transition to CMSSW-based software downstream. I propose that it may be easiest to fix this in firmware by delaying the orbit header until the "real" BX=0 appears. I add Rocco and Dinyar as "assignees" only so that they can receive the notification.