Add print method for 's2dv_cube'

Description in issue #128 (closed).

Test the function

library(CSTools)
source("https://earth.bsc.es/gitlab/external/cstools/-/raw/develop-print_s2dv_cube/R/print.s2dv_cube.R")
lonlat_prec

Output:

's2dv_cube'
Data          [ 1.2009e-08, 5.6514e-09, 0, 8.4771e-09, 2.6138e-08, 2.4018e-08, 0, 6.3578e-09 ... ] 
Dimensions    ( dataset = 1, member = 6, sdate = 3, ftime = 31, lat = 4, lon = 4 ) 
Coordinates  
 * dataset : exp1 
   member : 1, 2, 3, 4, 5, 6 
 * sdate : 20101101, 20111101, 20121101 
   ftime : 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 
 * lat : 47, 46, 45, 44 
 * lon : 6, 7, 8, 9 
Attributes   
   varName  : prlr 
   metadata :  
      prlr 
        units : m s-1 
        long name : Total precipitation 
        other : use_dictionary, description, daily_agg_cellfun, monthly_agg_cellfun, verification_time 
      lon 
        cdo_grid_name : r360x181 
        other : dim, data_across_gw, array_across_gw, first_lon, last_lon, projection 
      lat 
        cdo_grid_name : r360x181 
        other : dim, first_lat, last_lat, projection 
   Datasets  : exp1 
   Dates  : 2011-03-01 2011-03-02 2011-03-03 2011-03-04 2011-03-05 ... 
   when  : 2023-04-11 17:05:57 
   source_files  : /esarchive/exp/ecmwf/system5c3s/daily_mean/prlr_s0-24h/prlr_20101101.nc ... 
   not_found_files  :  
   load_parameters  : 
       ( var )  :  = prlr 
       ( exp )  : path = /esarchive/exp/ecmwf/system5c3s/daily_mean/$VAR_NAME$_s0-24h/$VAR_NAME$_$START_DATE$.nc 
       ...