EM watch http stream

[codeliner]

Follow up of #22

$eventMachine->watch(Stream::ofService('service_name', 'stream-projection-name'))

Event Machine should use a ServiceResolver to resolve a service_name to a service stream base url
In DEV mode a simple ServiceResolver uses the service name directly and assumes that the service is available within the docker network. In production the service resolver should use Consul/etcd or a registry provided by cloud infra.