Add support for quick calculations to Count/Unique e.g. cumulative sum based on count, difference based on counts

If you are working with a String column e.g. Product Name and you are looking at a unique count of product name by time, you can easily see how many unique products were sold e.g. per month. However, if you want to look at the cumulative unique products sold or the difference in unique products sold per month you do not have 'quick calculations' available.  You have to hand craft the necessary custom expression, which is non trivial for most users even advanced users.

Personally I work a lot with clinical data and there is a lot of counting and unique counting of entities e.g. count adverse events, unique count adverse events, count number of clinical trial sites, unique count number of patients enrolled in a trial.  All of these counts/unique counts need the same quick calculations as those provided for a  sum of Sales column e.g. Moving Average, Cumulative, Difference, YOY, etc.