Fixes a number of GiBUU things.
- GiBUU now has flux cut measurements correctly re-normalised.
- GiBUU cmake tweaks to smooth GiBUU set up.
- TotalIntegratedFlux and flux histograms are now only held by the InputHandler, wrapper methods are provided for Measurement classes.
- TotalIntegratedFlux should now correctly handle flux cuts which do not line up with the flux bins.