* Use multi step build to limit the image size
This change replace the Dockerfile with a multi step build to avoid huge image
size (the new image should be around 130Mo including all layers), compared to
more that 1Go with the full build chain. It's also more safe. This image does
not include cargo (not needed in production), so the old Dockerfile is available
and renamed Dockerfile.slim for those who use Docker for development setup.
* Use correct path for local repository
* Use sleep between chmod and execution
