Renamed actions for Normal distribution:

• InverseNormalDistribution -> NormalInvCDF
• NormalDistribution -> NormalCDF

New Actions for Poisson Distribution (requested by Julio Bittner)

• PoissonCDF - Computes the cumulative distribution (CDF) of the distribution at x, i.e. P(X ≤ x).
• PoissonLnPMF - Computes the log probability mass (lnPMF) at k, i.e. ln(P(X = k)).
• PoissonPMF - Computes the probability mass (PMF) at k, i.e. P(X = k).
• PoissonSample - Samples a Poisson distributed random variable.
• PoissonSamples - Samples a sequence of Poisson distributed random variables.
• PoissonSamplesFill - Fills an array with samples generated from the distribution.

Upgraded to a Service for Platform 11

Switched to math.net library for flexibility.