Makes graphs working without GNUPLOT

Use internal capabilites instead (the graphs have a small number of
points, so the compilation time isn't affected)

Fix spelling and other details
Merge pull request #118 from cassiersg/chimie3

Makes graphs working without GNUPLOT
Merge pull request #119 from anpar/master

Small spelling correction (q1/math)
Add INMA2380 by Yannick Tivisse