functionality
    **test support for one sphere**
    add support for two spheres
    implement ba inversion
    implement bs inversion
    improve Experiment __str__()
    improve Sphere __str__()
    include numba???
    get oblique incidence working
    
Documentation
    notebook for .rxt files
    notebook for no sphere inversion
    notebook for one sphere inversion
    notebook for two sphere inversion

command-line applications
    ad
    iad

