Added log form gnuplot showing how to display level-sets.

examples/hamilton-jacobi-parallel-map/gnuplot.txt

+tomas@tomas-linux:~/Desktop/VU_CPU_MAPA/work_dir$ gnuplot
+
+	G N U P L O T
+	Version 4.6 patchlevel 4    last modified 2013-10-02 
+	Build System: Linux x86_64
+
+	Copyright (C) 1986-1993, 1998, 2004, 2007-2013
+	Thomas Williams, Colin Kelley and many others
+
+	gnuplot home:     http://www.gnuplot.info
+	faq, bugs, etc:   type "help FAQ"
+	immediate help:   type "help"  (plot window: hit 'h')
+
+Terminal type set to 'wxt'
+gnuplot> set cntrparam levels 15
+gnuplot> set cntrparam bspline
+gnuplot> set contour
+gnuplot> splot 'u-00001.gplt'
+
+gnuplot> unset surface
+gnuplot> splot 'u-00001.gplt'
+
+gnuplot> set table "test.gplt"
+gnuplot> splot 'u-00001.gplt'
+gnuplot> unset table
+
+gnuplot> set table "test2.gplt"
+gnuplot> plot 'test.gplt' index 10
+gnuplot> unset table
+
+gnuplot> plot 'test2.gplt' 
+