Peruvian Flute Update: centered detector, reduced world size, space between rpd and tungsten block, removed all hits that are not optical photons

New physics list to allow for optical simulation. New materials class to describe optical properties. Update RPD geometry to better reflect reality. New test RPD to visualize photon propogation. New 'pan flute' RPD prototype

Addapted Mike's geant program for ZDC beam test 2018, this includes adding magnetic field, zdc class, rpd class, new particle generator, rpdhit/sd class. Also, began to make code more readable.

MonteCarlo folder now available. Same as from Mike Phipps repository, except for few adaptions for Geant4 compatibility with newer versions and CMakeLists.txt changes to have the folder as part of JCaPA