Update centos-art.sh to print documentation of global functions.
    
    - Previously, the centos-art.sh --help option was not able to receive
      a value. Only the centos-art.sh documentation manual could be
      printed when it was provided. This make impossible for global
      function documentation to be printed. This update changes the
      centos-art.sh script and the tcar_printHelp function in order for
      centos-art.sh script to print out global function documentation
      using the --help=filename.sh form. It is important that no space be
      between --help and filename.sh, otherwise the tough parser inside
      centos-art.sh script may be confused about whether filename.sh is an
      argument of --help option or an argument of centos-art.sh script
      itself.
    
    - The TCAR_MANUAL_FILE and TCAR_SCRIPT_DIR_MANUALS environment
      variables were removed from centos-art.conf.sh. Default values to
      this variables are set in tcar_printHelp function.