Filters, Transformations, and SummaryFeats

[duckduckdoof]

So far, filters, transformations, and summaryFeats are used to modify what is returned when requesting a specific Doc/Token feature from this module. While we want to preserve the functionality, the way the code was written to retrieve them is hard to follow, and a bit clunky (since not all features have the same set of filters, transformations, etc.).
We need to rewrite how this is implemented which is properly documented and easy to understand in the code.