Moving the reset_h0 functionality to baseline
Currently resetting the h0 value happens at the spectrum level (in Omega_spectra module) and hence one has to call the rest_h0 twice to reset point_estimate_spectrum and sigma_spectrum. However we expect both those quantities always to have the same h0 value, so calling twice to do that seems bit strange.
Also this doesn't rest the point_estimate and sigma quantity in the baseline object that is already calculated using the old point_estimate_spectrum and sigma_spectrum. So one need to call the postprocessing subfunction to recalculate the point_estimate and sigma for the newly scaled point_estimate_spectrum and sigma_spectrum. If we have the ho_reset at the baseline level, then calling the reset_h0 can reset all the relevant quantities in the baseline object.