loadGammaListed loads standards from SnP files.
gamma_listed = loadGammaListed(filenames,freq_desired)
inputs:
filenames: cell list of filenames of the standards
ex: {'stds/open.s1p','stds/short.s1p','stds/load.s1p'}
freq_desired: frequency vector for interpolation of data (must be in Hz)
outputs:
gamma_listed: [3,num_pts] complex reflection coefficients of OSL in
same order as filenames