Simplifies DD4hep code now that /world is the default path
in particular drop a lot of ifdef DD4hep dedicated to adding /world
Part of set of MRS !3785 (merged) Lbcom!628 (merged) Rec!3123 (merged)
Edited by Sebastien Ponce
in particular drop a lot of ifdef DD4hep dedicated to adding /world
Part of set of MRS !3785 (merged) Lbcom!628 (merged) Rec!3123 (merged)