Polyblur: Removing mild blur by polynomial reblurring

This is an inprovement on unsharp masking. Instead of subtracting a blurred version of the image, the particular blur kernel is estimated, and unsharp masking is performed as a linear combination of repeated iterations of that blur. Besides the estimated gaussian kernel params there are two additional params α and β, affecting the coefficients of the original image and the different iterated blurs.