Save T2 in mat files

Change to Method_2d_quasiphase.  There is a change of the value
n_fit_points in phasing2dPP, but I don't know the purpose of this.
reduce number of fit points for phasing2dPP

As part of the fix of the phasing problems, reduce the number of points
in the frequency domain used to fit the slope of the spectral phase from
the FFT analysis of the single channel interferogram
update quasiphase

update method_2d_quasiphase to use the new phasing procedure