Make sample_width, bin_size, diffusion & drop_dist tuples

[jwaiton]

All these parameters involved in Beersheba are of fixed size and we don't want them to be changed once they're assigned (immutable). Hence it would be beneficial to convert them to tuples as it would ensure they aren't altered in the running of the cities.

All of these parameters are defined within the beersheba config, but converting them all will require ensuring that all functions in which each variable is used is altered across the entire repository.