Initial commit for distribution package. Contains Exponential, Laplace, ...

...Normal, and Uniform
Consider "ExcessKurtosis", since most of the other functions do not abbreviate and "Ex" may not be immediately obvious. The few that do abbreviate are "Prob" and "LogProb" which is more immediately obvious that they are shorthand for "probability". The other that is abbreviated is "StdDev" which would be very difficult to misinterpret.