add flag for controlling EventInfoBeamSpot decorator alg
Under certain circumstances (ZDC calibration data was the particular use case which highlighted this) is may be neither possible nor necessary to run the EventInfoBeamSpotDecoratorAlg. This flag adds the possibility to explicitly disable it.
InDet was felt to be the most appropriate place for this after discussions in the Reco meeting.
The way we might want to handle this in ComponentAccumulator-based config is still being discussed.