Changes
 
v0.4.3: updated template.grb so that code table 4.3 is changed from undefined to forecast
          This will eliminate wgrib2 warnings.
        updated g2grb.gs: better error messages
        updated g2grb.gs: template.grb is placed in $GASCRP instead of $GADDIR
            Ubuntu installation (v20.04 LTS):
               if $GADDIR is undefined, GrADS finds the system Cairo library
               if $GADDIR is defined, GrADS looks for the Cairo library
                  Therefore the user has to setup the tables that define the
                  location of the libraries. People are unhappy.
               Therefore put template.grb in the $GASCRP directory.  People rejoice.