Operation to add a new dimension in a file
addDim(values, ncfile, dimn)
values= [size]
[size]: size of the dimension ('unlimited' for unlimited)
ncfile= name of the file
dimn= name of the new dimension
$ python ${pyHOME}/nc_var.py -o addDim -S 128 -f SouthAm_Climzones.nc -v Lstring