addVar(values, ncfile, varn)
values= [dnames]|[varattributes]|[kind]
  [dnames]: [dimn1],...,[dimnN], ',' list of name of dimensions for the new variable (already existing)
    'scalar', for scalar variables
  [attributes]: [std_name]@[long_name]@[units], standard name, long name and units of the variable ('!' for spaces)
    'None' for no standard attributes
  [kind]: type of variable (standard netCDF4/C-like values, 'c', 'i', 'f', 'f8',...)
ncfile= name of the file
varn= name of the new variable