minimum wavelength criteria

[dylanmikesell]

It seems like the minimum wavelength criteria is only actually function in iftan.py (e.g. line 166 idxx = np.where( float( _minWL.get() ) < dist/(disper*per) )[0]), but not in ftan.py. Therefore, the cutoff based on minimum wavelength is not being propagated into the data for ANSWT.py. I do not see any sort of wavelength filtering in prepare_tomo.py either. Should this be added to ftan.py?