Docker aggregation

mine.docker outputs a series of lists of ip:port pairs of docker containers, grouped by docker image.

Here's an example of output:
```
root@boucha:~/salt# salt 'davedocker01' mine.get_docker cidrs='["107.170.147.0/24", "172.17.42.0/24"]'
davedocker01:
    ----------
    dockerusername/apache:latest:
        ----------
        ipv4:
            - 107.170.xxx.xxx:8080
            - 172.17.xx.x:8080
            - 172.17.xx.x:80
            - 107.170.xxx.xxx:80
```