Documentation updated properly.
3D Cartesian geometry also tested.
Documentation updated properly.
Added weighting probability in the injection of particles.
Fixed an issue in which some particles in the corner were interacting
with the axis boundary. Now the axis acts as a reflective boundary in
case a particle is wrongly assigned to it.
Unification of boundary conditions into one file.
Some changes to input file for reference cases. This should have been
done in another branch but I wanto to commit to save progress and I
don't want to deal with tswitching branches right now, I'm very busy
watching Futurama.