Creates a bar chart with error bars using ggplot2::geom_col.
plot_barchart(x)Returns an object of class ggplot and prints it to the
graphics device.
Data frame with columns par or parameter containing
the name of the parameter, q2.5 or q2_5 for the 2.5 percentiles
(i.e. the lower values for the error bars), median for the median
values (i.e. the height of the bars) and q97.5 or q97_5 for
the 97.5 percentiles (i.e. the upper values for the error bars).