PLOT: added custom value plots
PLOT: added custom distribution plots
PLOT: added custom nodevaluelist plots
PLOT: log output clean up
PLOT: added safe behaviour for faulty plot configs
PLOT made custom plot examples to comments in cfg
PLOT: added gnuplot datetime functionality
PLOT: plot-class clean-up - removed old stuff
PLOT: plotting-class clean-up - rem. old stuff
PLOT: moved PlotStyle enum to PlotData class