bands.x writes a file filband.'gnu' with bands in plottable format (by gnuplot
or xmgrace or whatever plotting program). Saves a step (the plot_bands.x run)
when plotting bands: useful for tutorials ... 


git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@11076 c92efa57-630b-4861-b058-cf58834340f0