code: function cacheStepProperty(that, gameStage, property, value) {
          if (!that.cache[gameStage]) that.cache[gameStage] = {};
          that.cache[gameStage][property] = value;
      }
docs: ## Helper Methods 
  ### cacheStepProperty
  
  Sets the value of a property in the cache
  
  Parameters are not checked
  
  @param {GamePlot} that The game plot instance
  @param {GameStage|string} gameStage The GameStage object,
  or its string representation
  @param {string} property The name of the property
  @param {mixed} value The value of the property
  
  @see GamePlot.cache
  
  @api private