Show one line in plot2AUFC by default

[k1o0]

In psy.plot2AUFC only one line should be plotted during the 2AFC experiments. Perhaps the panels could call psy.plot2AFC then switch when contrast discrimination conditions occur? Could also check the parameter set during build. Regardless, the three lines should only be shown when there is contrast detection with no-gos, as the plot changes for contrast discrimination anyway.