Add sample data from C. Leibig

Thanks!
gen-demo-data: support for saving Leibigs data
nix-plot: also ignore old versions of ggplot
Replace relacs generated data file
Move Plotter() to plotting.py
Add inital version ipython notebook for INCF TF
gen-demo-data: cosmetic changes to leibig data
plotting: simple support for setting x (1d-set)

Support for non 1d-set case is missing
INCF TF IPython notebook update
Update INCF TF IPython Notebook