Handle LAN Docker-registry with various setups

Docker image `dolphm/network-tools` is used to check 
connectivity from other containers 

## Useful stuff

* Stuff handled by docker-compose (networks, volumes, ..) is by default named 
after the root directory
* When a Docker network is setup, the IP address returned for 
<machine_name>.local changes from 192.168.x.x to the address of the local Docker 
network.  

## Documentation

* [Deploy a Docker registry](https://docs.docker.com/registry/deploying/)