Loads all the images and documents in the dirName folder to DcsBuffer.
String The name of the folder to load files from.
If there are images and documents in DcsBuffer, to call this function, all the data in DcsBuffer will be cleared and the new data will be loaded again. If dirName folder doesn't exist, exveption DcsFileNotFoundException will be thrown. If dirName is nil or '', exception DcsValueNotValidException will be thrown.