Blochwave : Enable user input of structure factors and excitation errors

[ronandrevon]

User provides inputs for the complex amplitudes of the diffracted beams of interest and their deviation parameters, and get an output of their complex amplitudes after propagating through a certain crystal thickness.

This can currently only be done manually by specifying the beam info to a created Bloch object b0.
The info should currently be provided in a pandas Dataframe format to member b0.df_G.
Since assembling requires structure factors for beams that are not part of the simulations these would also have to be provided into member b0.Fhkl.
After that calling the method b0.solve(thicks=(t_ini,t_end,n_thicks)) should provide the intensities as a function of thickness which can be seen calling b0.show_beams_vs_thickness()