EIC code displayed by LXR

This example demonstrates integration of the navigation elements of [VecGeom](https://gitlab.cern.ch/VecGeom/VecGeom), to investigate the performance benefits.
This integration is in development. Supporting Placement volumes -- other volumes would be handled by existing Geant4 navigation.
The example loads a GDML file for the geometry, and can execute a batch file (vecgeomNav.in) or run interactive commands or both.

SEE ALSO: README