Update feature spreadsheet

This is a simple PR that mainly updates our excel spreadsheet of features to reflect the current status.

In determining that status, I also added unit tests for fluent functions (which just work!) -- so I've included them in this PR as well.

Submitter:

[x] This pull request describes why these changes were made
[x] Code diff has been done and been reviewed (it does not contain: additional white space, not applicable code changes, debug statements, etc.)
[x] Tests are included and test edge cases
[x] Tests have been run locally and pass
[x] Code coverage has not gone down and all code touched or added is covered.
[x] Code passes lint and prettier (hint: use npm run test:plus to run tests, lint, and prettier)
[x] All dependent libraries are appropriately updated or have a corresponding PR related to this change
[n/a] cql4browsers.js built with npm run build:browserify if source changed.

Reviewer:

Name:

[ ] Code is maintainable and reusable, reuses existing code and infrastructure where appropriate, and accomplishes the task’s purpose
[ ] The tests appropriately test the new code, including edge cases
[ ] You have tried to break the code

cqframework / cql-execution