WIP: Add draft AUP

Open Ernst van Nierop requested to merge evn-draft-aup into master

Closes https://gitlab.com/gitlab-com/infrastructure/issues/56

This is a first draft and is effectively mostly copied from AWS: https://aws.amazon.com/aup/

I wonder if it is required / nice to acknowledge AWS's role here? In any case, we'll be making edits that are more specific to GitLab from here on.