Normal random number generator

This device produce periodically a number randomly with a normal law. To generate it, it uses the Box-Muller methods. To generate the necessary uniform distributions, it uses the park and Miller method.

seed: The seed represents the seed of the generator. A same seed will produce the same set of number.

Ts: At each time step of Ts, the random number generator will compute another random number.

variance: The variance represents the law variance.