Graphing utility for eDeploy - First commit

This tool consists of a graphs and reports library, and a CLI to
generate graphs based on the results of eDeploy's healthcheck test.

The graphs are generated with gnuplot.
boxplot graph added
Adds support for multiple input files, in the form of a POSIX filter
cleanup of temporary files
prettier output, first attempts
Improvements in x-axis ordering
grapher: Adjust range from 0

It's better starting Y range from 0 to insure a better comparaison
between values. Automatic scaling make you think you have big
differences while it's not the case
grapher: Filled histograms to ease reading

Transparent histograms were hard to read. Filling them help having a
quick read.