Update svg functionality:
    
        - Rename OPTIONNAM and OPTIONVAL variable names to ACTIONNAM and
          ACTIONVAL respectively.
    
        - Inside svg_vacuumDefs and svg_updateMetadata functions, add
          positional parameters interpretation using getopt(1), re-define
          regular expression to match scalable vector graphic files only,
          and use cli_getFilesList to define list of files to process.