Added DCSteppingAction class. Adds the energy deposited in the scoring volume to the DCEventAction object for every step.
Major commit since I forgot to - added the DCPrimaryGeneratorAction class, which for now generates monoenergetic neutrons in the x direction. I commented out some of the geometry to simplify things into just a single polyethylene box in the middle of the World container, which is full of air. The box, eventually to become the irradiator box, is the scoring volume and the simulation calculates the dose in it. Tested successfully with the visualization and running a few hundred events. Next steps are to add the other geometric shapes, make the source extend to a full container and use a provided neutron spectrum. The dose scoring volume will be moved a small tissue box that will be placed outside of the irradiator.