Update standalone build and add /minimal folder for a cmake compilation of application loading LHCb geometry and dd4hep simple python loading to derive a TGeoManager to use further

@bcouturi i played a bit with standalone_build branch and i think i managed to have simplified scripts and CMake project after sourcing the Detector project alone on top of your branch. Maybe you want to update first standalone_build with master and then merge the minimal example from this branch?

If you have suggestions on how to load also the Magnetic field map from LHCb directly in the minimal example it would be great.