Add definitions for 4 keys operationalization

[davidstanke]

Currently, these are implicit in the queries used in Four Keys (as well as spelled out in words to some extent on that site). Let's put those on this site, to extract the definition from the implementation.

[davidstanke]

Here's one of them: https://docs.google.com/presentation/d/1O53trUjYkmEQuz4u7fUgzzdqS5YUQaJj3TbN4h9HdRs/r/0-cc_1jb33OzkgcSQQrhV1bQ/edit#slide=id.p

[davidstanke]

Community document for ongoing conversation: https://docs.google.com/document/d/10v67Pm9C9UWKV89YYP6eCI0bOxHhvFbpFdRvUnjagsI/edit#heading=h.nky4wm55k4ee