Docker Container Env vars are not injected

Currently only operation inputs prefixed by `ENV_` are injected as environment variables of a container. It could be interesting to inject also static environment variables coming from the container application and known as [`docker_env_vars`](https://github.com/alien4cloud/docker-tosca-types/blob/1ec559e27c0b7a8704df2ac24f7dc372b5809795/docker-types/types.yml#L134).
