Evaluate copyright license agreement and add top level LICENSE.md

[wdconinc]

Cernlib license

(C) Copyright CERN except where explicitly stated otherwise. Permission to use and/or redistribute this work is granted under the terms of the GNU General Public License. FLUKA routines included in GEANT3 are joint copyright of INFN and CERN and are not licensed under the GPL: permission to use and/or redistribute outside GEANT3 should be negotiated. The software and documentation made available under the terms of this license are provided with no warranty.

I think the statement "permission to use and/or redistribute outside GEANT3 should be negotiated" (bolding added) maybe puts us in the clear.