* First steps toward refactoring Statistical Distributions into smaller classes: BETA() and GAMMA() (and related functions) to start with... they all need a lot of tidying up, and more testing; but it's a start
* Add basic datatype validations to Beta and Gamma Excel function implementations
* Switch to using a trait with the validation methods to provide easier sharing between distribution classes
* Additional unit tests for Beta and Gamma functions, including unhappy path for validations
* Extract ChiSquared functions
* Additional argument validation checks with unit tests for Chi Squared functions
* Extract Fisher
* Move MEDIAN() and MODE() to the Averages class
* Extract filters for Median and Mode for common usage
* `GAUSS()` and `GAMMA()`, `NORM.S.DIST()`, `LOGNORM.DIST()` and `F.DIST()` function implementations, and further unit tests for a number of the statistical functions
Co-authored-by: Adrien Crivelli <adrien.crivelli@gmail.com>
Mark Baker