Feat/filepicker

Users can upload a photo through filepicker, post it to our Amazon S3 bucket. A URL to the photo is returned upon success. We need paths to store this link for each user in our own database. That should give us working avatars.  I am adding the credentials for S3 and Filepicker to our shared folder.

The photo in this commit is meant to serve as a "default avatar" for people who don't have one yet. We will want to remove it before launch, but it helps for testing.