If min val > 100, start CDF axis at nearest 100.
Don't use cutoff for mean_span combines.
Fix totals_loss plot for voip-rrul test.
Add cdf_combine to http-{1up,rrul} tests.
Support --norm-factor for normalising plots (bar plots only so far).
Support 'group_by==both' for *_combine plots (warning, here be hacks).
Add bar_combine type==both to http-* plots.