ExtG4 Orientation : Translates Geant4->GGeo only

X4 Class names mostly correspond to Geant4 classnames

top level translator
converts many G4VSolid primitive shapes (sphere, box, polycone, ellipsoid, torus, …) into npy/nnode : either single nodes or trees. There is not a one-to-one correspondence, with Opticks tending towards trees to avoid having to implement too many primitives in CUDA.