se: Change point size

This patch changes the point sizes so that lower points are larger than
higher points. This makes more intuitive sense since convergent search
algorithms will tend to minimise the number of points in the lower
regions, making them harder to spot; and maximising the number of points
in the higher regions, causing them to clump together and overlap.
se: Implement Gaussian measurement noise using

This patch adds a Gaussian noise generator which can supports up to 25%
measurement error. Credit to the amusing but tastless:

    http://www.protonfish.com/random.shtml