Keep the Docker image small

[AndreMiras]

Is your feature request related to a problem? Please describe.
The docker image is 1.8G, making it lighter would make it easier to publish, refs #23

Describe the solution you'd like
We could leverage multi-stage builds.

Describe alternatives you've considered
Doing it the old fashion, deleting things as we use them for each layers, but it's harder to deal with.

Additional context
Tested in the current main c897403, this is the result of a docker build then a docker images command