sigc::slot<std::string> _get; ///< slot to get the configuration variable's value
sigc::slot<bool, std::string> _set; ///< slot to set the configuration variable's value
sigc::slot<std::string> _get; ///< slot to get the configuration variable's value
sigc::slot<bool, std::string> _set; ///< slot to set the configuration variable's value