Update centos-art.sh script `shell' functionality:
    
        - Start using --update-copyright instead of --update-topcomment.
          Because we do not modify to comment completely but the copyright
          note and license section, --update-copyright seems to be more
          appropriate.
    
        - When OPTIONVAL/REGEX build a valid regular file, use that file
          as unique file inside list of files to process. Otherwise, REGEX
          is considered as a regular expression that should match file
          path inside OPTIONVAL directory. This way, in order for a file
          to be inside the list of files to process it should match REGEX.
    
        - Add verification to list of files to process. If this list is
          empty there is nothing to do except print a message and end
          script execution.
    
        - Start using one dimensional array variables inside
          svg_updateTopComment in order to handle copyright information.
    
        - Function name shell_updateTopComment was renamed to
          shell_updateCopyright. The file name will be renamed to
          shell_updateCopyright.sh further.