Version 1.3.21 released

Add an ImagesComparator class to compare two images
Add an ImageColorAverager class to compute the average color around a pixel in an image
Add an DeltaEDistance class to compute the distance between two colors
Add a setFileView method for both the JFileSelector and the JMultipleFileSelector
Add an ExtendedStringTokenizer which is able to keep the empty tokens during the iteration
Fix some cases where the prefixes of a Node in the XMLTreeHandler would not be correctly bound