boxPlot: Render box plot charts from data sets

This class can be used to render box plot charts from an array of data.

It takes an array with the values to plot and makes the necessary calculations to determine the positions of the boxes rendered in the chart.

The class generates an image of a given width and height and stores it in JPEG format file.

In this new version, you can render more than one data array and add a series names in each bloxplot.

You can also display some statistic information about each series.

Finally we fixed some bugs in boxplot draw algorithm.