Gaussian noise symbols

[jamesturner246]

Noise symbols ε are currently all uniformly distributed in [-1, 1]. The possibility of having ε normally distributed about 0, with standard distribution σ, might also be useful, for statistical applications.

Normally distributed ε could be stored and computed in a separate array, in a similar manner to uniformly distributed ε. All σ for each ε would need to be stored globally.