Integrate into keystone-test-project

[radiovisual]

Per the conversation with @JedWatson on Slack (#dev):

To get the new S3 storage adapter that josephg contributed integrated into keystone-test-project:

Steps are [basically]:

• [ ] add the keystone-storage-adapter-s3 dependency using the git url to the test project’s package.json
• [ ] if (and only if) S3 environment variables are present, create an adapter in the Files list and add a field that uses it
• [ ] edit admin/client/utils/List.js and remove both instances of /legacy (this will switch you over to the new api)
• [ ] load the Admin UI, make sure the new field works as expected (upload / remove files, check they exist in S3 with the correct headers, etc)

@josephg , I can take this on if you are not already working on it?

[radiovisual]

I should have opened this in the keystone-test-project repo, so I will close here, and re-open there.