Add option to add random normal noise to Laplacian filtered image

[Yu-AnChen]

When the edge amplitudes (Frobenius norm of the laplacian/LoG filtered image) in the overlapping pairs are low, our registration will yield low errors, which, in general, are not "correct". We compute edge amplitudes of all the permutation tiles and find the minimum edge amplitude needed to generate confident registration error (triangle threshold proposed). During registration, we add random noise of the found minimum edge amplitudes to the image overlaps. The errors from the noisy images are more robust when the background of the scan is mostly the same value (usually image is saturated or all zeros).