CST_SaveExp needed developments

I open this issue since @nperez has detected some developments needed in CST_SaveExp:

1. • There is at least one element in the metadata on the NetCDF that is not saved properly. That is $lats_range (lons_range) that it is a vector of two values. It only appears 1 in the output:

In the object we have

[...]
$metadata
$metadata$region$lats_range
[1] "20" "80"

But in the saved NetCDF we see:

        int region(region) ;
                region:name = "NAO region" ;
                region:lats_range = "20" ;

2. • Some warnings appear but they are not necessary regarding spatial coordinates:

> CST_SaveExp(data = nao$hcst,
+           destination = file_dest, 
+           dat_dim = NULL, sdate_dim = 'syear', 
+           ftime_dim = 'time', var_dim = NULL, 
+           memb_dim = 'ensemble')
Warning messages:
1: In SaveExp(data = data$data, destination = destination, Dates = data$attrs$Dates,  :
  Spatial coordinates not found.
2: In SaveExp(data = data$data, destination = destination, Dates = data$attrs$Dates,  :
  Parameter 'startdates' should be a character string containing the start dates in the format 'yyyy-mm-dd', 'yyyymmdd', 'yyyymm', 'POSIXct' or 'Dates' class. Files will be named with Dates instead.

3. • See if the following development could be inculded:

Multiple dimensions of length 1

dim(nao$obs$data)
  region    syear ensemble      dat      var     sday    sweek     time 
       1       24        1        1        1        1        1        1 

nao$hcst$data <- .drop_indices_dims(nao$hcst$data)

Here there is a function to drop the dimensions.

Eva