code: function(logger){
  		// add listener to the logger methods
  		logger.onlog.addListener(Log4js.bind(this.doAppend, this));
  		logger.onclear.addListener(Log4js.bind(this.doClear, this));
  	
  		this.logger = logger;
  	}
docs: Set reference to the logger.
  @param {Log4js.Logger} the invoking logger