Add full CloudFormation stack configuration for AWS resources

Setting up 'serverless' functions like the Lambda function this module uses at its core can be a bit tricky. In my first go, I was planning on documenting the 25 or so steps to successfully set everything up in the AWS console... but I thought better of that.

Instead, I'm planning on providing a complete CloudFormation stack template (as a .yml file) which can be used to quickly build the required resources, e.g.:

• Lambda function that scans an image with Rekognition and sends data to Drupal.
• Trigger for said Lambda function (whenever a file is added to an S3 bucket).
• S3 bucket which stores Drupal images (using S3FS), and has said trigger attached.
• Lambda Permission and IAM Role required to tie all the above together and allow the S3 bucket and Lambda to interact with Rekognition.