Create an automatic build environment on AWS

[aureq]

This issue is related to #62

Matomo needs a better and fully/mostly automated build environment. This issue is to track that work.

• Manually generate an EC2 instance from a vanilla AMI
• Record the list of installed packages and specific commands
• Record the deployment process for Matomo's package
• Secure and automate the GPG keys handling, SSH private key and remote server public keys (using S3 and KMS)
• Create a bootstrap script to include all the above
• Create a CloudFormation template to deploy an EC2 instance and inject the bootstrap script
• Push the resulting .deb into debian.matomo.org for publication