Make analyses simpler and more modular

[kyrsjo]

Two problems:

• RootFileWriter is HUGE
• ROOT + Geant4 is a pain.

To fix this, we basically need to rewrite the whole rootfilewriter, splitting off code and sending it to other classes.
Furthermore, we should consider to use the "new" analysisManager tool, instead of directly linking ROOT.
See:
https://indico.cern.ch/event/776050/contributions/3241822/attachments/1789267/2921102/Analysis-v3.pdf