Add a Makefile and a Dockerfile which automates the build and release steps

[ccojocar]

The following build commands are supported:

Build:
make

Run tests:
make test

Make a release:
make release

Make a release and build the docker image:
make image

Publish the docker image:
make image-push

[pataquets]

Strongly against Docker image publishing via docker push vs. using Automated Builds from source on Docker Hub as an official Docker release method.
Automated Builds create image tags from git tags & branches and provide code traceability, opposed to docker push'ing.
See #372 and #460.