New TGeoParallelWorld class supporting navigation in a parallel flat node. Currently the parallel world is made by TGeoPhysicalNode objects which has to match paths in the active geometry. Coupling navigation via TGeoManager::SetSetUseParallelWorldNav(true) will prioritize the parallel world objects with respect to the ones in the real geometry.

(cherry picked from commit 2a7c470af52e9bf931f20cc27fe8ea1e280b0bfe)
Fixes for the new parallel world navigation feature with a tutorial macro

(cherry picked from commit 2c7ca5526c5bbf40951dd40da6dc88af118dfbd6)