Make AnalysisHelpers part of the DaVinci Stack

Hi all! Whenever a new OpenData request is created (the Ntuple Wizard is currently only open to LHCb members) and that request is submitted for production on Analysis Productions, we have to also push a directory AnalysisHelpers with some basic (and fairly static) python code. This is somewhat inconvenient for us and also the maintainers of Analysis Productions (see the open issue here)

After some discussion we have decided it is best if we make this package part of the DaVinci stack. I'm not quite sure how that works though. Can you point me in the right direction? @masmith Many thanks!

(also tagging @erodrigu and @dfitzger so they can follow the progress)