Implement Shannon Entropy Macro

[Matts52]

Implement a macro that calculates the shannon entropy for categorical columns. Something like the following would likely do it:

    -sum((count({{ column }}) over (partition by {{ column }}) * 1.0 / count(*) over ()) 
        * log(count({{ column }}) over (partition by {{ column }}) * 1.0 / count(*) over ())) over ()