al file name or a URL  or
                   b. An 'msstate.cstm.data.JDataset' object, which is the reference to already
                   open netcdf file.  [ncRef=msstate.cstm.data.JDataset(uri)]
           var  = variable or 'global'     
           attrb = global or variable attribute name  (case ignored)

           [attr]= njGetAttributes(ncRef);                 Returns only 'global' attributes
           [attr]= njGetAttributes(ncRef,'global',attrb)  returns a variable with the value of a global at