Add SIFT processor

[yuripourre]

OpenIMAJ code:

	final FImage image = ImageUtilities.readF(OpenIMAJ.getLogoAsStream());

	final DoGSIFTEngine engine = new DoGSIFTEngine();
	for (final Keypoint keypoint : engine.findFeatures(image)) {
		System.out.println(keypoint);
	}