Added a simple hello world docker run test, docker name prefixes, CI runs docker. #14

This is a step of #14 (closed)

• Added a simple test that runs a docker container on the target environment
• Added north.config.docker_url and north.config.docker_name_prefix to configure the target docker environment
• docker_name_prefix has to be used on all containers. All containers need a name and this as prefix. You have to assume that the target docker environment might run other services.
• The tests will clean up all container with the configured docker_name_prefix
• Also added a the architecture image to readme as a bit of documentation