Issues with Utilities/Probability

[JCRPaquin]

I've been extending Utilities/Probability for a little bit with additional probability distribution sampler functions and have a couple of gripes:

• As far as I can tell Utilities/Probability is currently a normal distribution single-sampler and doesn't actually deal with larger concepts involving probability. This makes the module name appear to be a misnomer. I propose that it be renamed Utilities/Distributions, Utilities/Stats, or something similar.

• Further, the inclusion of the Distribution suffix in the module's functions is redundant. We already know that the module is about "Probability" and so exported function names should be obvious.

• BoxMuller is an implementation detail that should not be exposed to module consumers.

• Using single-sampler functions, functions that only sample one value from the distribution in question, does not allow us to abuse the strengths of accept-reject sampling methods to their fullest.

[Quenty]

TODO: Rename to Stats, remove redundancy.