Update quantile logic
if --quantile is not specified when calling mcvt-estimate-psd-quantile, default to uniformly spaced grid (0.0 - 1.0 spaced by 0.01 : percentiles).
if --quantile is not specified when calling mcvt-estimate-psd-quantile, default to uniformly spaced grid (0.0 - 1.0 spaced by 0.01 : percentiles).