statistical plots

[Jean Bréfort <jean brefort normalesup org>]

Hi,

With more time available during the twomonths to come, I'm going to work
again on histograms and probability plots. I'm wondering if I should
create families for each plot types or put all statistics related (at
the moment boxplots, histograms and probability plots) in the same
family or have three families (and probably more in the future). 
If we prefer one family for each plot type, I'll add icons for each
supported distribution in the probability plots family, otherwse, I'll
add just one which will use the normal distribution law by default. In
all cases, the distribution will be a (string) property of the plot so
it can be changed.

We also might rename the plot_boxplot plugin which implements all these
plots to plot_stats.

Any comment(s)?

Cheers,
Jean