Update `trunk/Scripts/centos-art.sh' file:
    
        - Update comments.
    
        - Start using `declare -xr' to define variables.
    
        - Introduce CLI_WRKCOPY variable to store the working copy
          absolute path.
    
        - Verify the working copy directory. Be sure it is
          `/home/centos/artwork'.  Otherwise, end the script execution.
          We cannot continue if the working copy is stored in a place
          other than `/home/centos/artwork'. This restriction is what let
          us to reuse contents using absolute paths inside a distributed
          environment like that one provided by The CentOS Artwork
          Repository.