Docu Driving Function

[fs446]

taken from #117

The equation contains only one omega not omalias. We should think about how to best integrate the pre-equalization filter. One idea is to introduce a function for it, that deoends on omega and omalias and reference to the formula given in the docstring of wfs_25d_preeq for a reference?

H(w) is aready defined in the docu of preeq_25d, we should modify all relevant Latex-equations to include it.