FEATURE: Download spreadsheet

[alwillia]

Provide a link in the documentation and/or test area (location TBD) for downloading an excel spreadsheet that is prepopulated with the function call. This is particularly useful for extracts: the user sees the data they want, they see a download button, and when they download it, they get a spreadsheet with the function call, not hard-coded data values.

This gives the user something they can relate to (downloading a sheet), but done is done in the new way with a function call, and is also good for extending the use since spreadsheets tend to get emailed.