Wrapping blue noise could maybe be generated faster

[benfrankel]

WrappingBlueNoise's algorithm is currently implemented as a minor variation on BlueNoise's algorithm, with sampling and distance calculations wrapping around the edges of the box. Since the distance calculation happens very frequently (up to 25 times per sample), it may be worthwhile to optimize it.

This could be done by putting a 2-thick border of cells around the grid, so that points near the edges of the grid are duplicated on the opposite edge. This would allow WrappingBlueNoise's distance calculations to be identical to those of BlueNoise. This approach would use more memory to make insert_point() slower and distance() faster.