VALUE = g_config (NAME, [, NEW_VALUE]) - Get/set settings of g_XYZ functions
NAME can be one of
"gnuplot_version" : Gnuplot version, e.g. [MAJOR, MINOR, PATCHLEVEL]
This parameter cannot be set.
"gnuplot_program" : Gnuplot program that is called in g_plot()
Default is "gnuplot"
"eps_viewer" and "png_viewer" : Programs called to view eps or png plots.
Defaults are "gv" and "eog".