Utilities for AWS S3

As I work on my contract with New Energy Risk, I am posting some of the useful publically-shareable functions that I use.

Functions for Copying CSVs and Models to and from AWS S3

The four functions in this file can be used to (1) load CSV and model files from AWS S3 and (2) upload CSV and model files under 5 GB to AWS S3. I added comments to clarify the terms for newer users of S3.
Co-authored by Paul Brit, [email protected], https://github.com/pbrit.