Add new test image

Busy image
Added contrast switch

For high contrast images the highest eigenvalues can be scaled up to
reduce the compression artifacts. With this option a 256x256 B&W letter
image can bee reproduced almost exactly with a k of only 16
Implement contrast from svd.py
Copied avd-avg to make pixelator
Clean up SVD pixelate
Converges on an idealized A