plot.bootstrapfit errorband fails if ylim is decreasing

[christianegross]

In plot.bootstrapfit, the plotting of the errorband is not done properly if the "upper" ylimit is smaller than the "lower" ylimit.
If we want to change this, we need to change the consistency checks on the errorband to account for two possible cases, ylim[1] < ylim[2] (default) and ylim[2] < ylim[1].
I do not know if we need this, but it is nice to be aware of this when not seeing an errorband.