[RFR] Introduce Ambassadors

Allows to use Docker through 2 distants servers

Local:
```yaml
applications:
    redis-cli:
        type: index
        image: vieux/redis-cli
        environments:
            REDIS_PORT_6379_TCP_ADDR: 192.168.56.6
        ambassador:
            type: local
            port: 6379
```

Distant:
```yaml
applications:
    redis:
        type: index
        image: dockerfile/redis
        ambassador:
            type: remote
            port: 6379
```