Utility programs for processing Grid magnitudes (charge densities,
potentials...). The most relevant are:

grid2cdf:   Convert from standard binary format to netCDF format
cdf2grid:   Convert in reverse

cdf2xsf:    Generate an Xcrysden "xsf" file directly from a netCDF grid file.

cdf_diff:   Generate a "difference" netCDF file for a system composed of
            two parts:  diff = Total - part1 - part2


grid2val:   Computes values of grid magnitudes at arbitrary points.
grid2cube:  Converts to Gaussian Cube format

