Ahodges/documentation/doc764

@WatsonEmily , please distribute for PM review for usability by our audience.
@jhelbert , @stroilova , @shnayder , @rocha  please review for accuracy, completeness, and level of detail, particularly wrt data czars who will need to revise scripts for post-download processing.
@mhoeber , @srpearce please copy edit.
Change this sentence to use imperative ("To download daily event files, open the **edx-course-data** bucket, and then navigate through the following directory structure to locate the files that you want")