remove volume fraction input to kappa aerosol mode

[claresinger]

for kappa aerosol mode, you shouldn't need to specify volume and mass fractions separately. better to specify mass fractions and densities (like for B formulation) and then calculate the volume fractions in backend instead of making the user do this.

[claresinger]

e.g. see how it is currently done here https://github.com/CliMA/CloudMicrophysics.jl/blob/ces/ARGplots/docs/src/ARGplots.jl