local_ip is not necessarily external ip
e.g. when running in a docker, the `local_ip` is in the docker range:

```
[1/23/2020, 3:19:39 AM] [HomeMatic CCU] local ip used : 172.19.0.2. you may change that with local_ip parameter in config
```
However, since docker proxies the ports, that address is not available externally. Specifying the external ip as `local_ip` results in an error binding, as that interface is not available in the container namespace:

```
homebridge_1  | [1/23/2020, 3:18:41 AM] [HomeMatic CCU] Creating Local HTTP Client for CCU RPC Events
homebridge_1  | [1/23/2020, 3:18:41 AM] Error: listen EADDRNOTAVAIL: address not available [redacted]:9090
homebridge_1  |     at Server.setupListenHandle [as _listen2] (net.js:1292:21)
homebridge_1  |     at listenInCluster (net.js:1357:12)
homebridge_1  |     at doListen (net.js:1496:7)
homebridge_1  |     at processTicksAndRejections (internal/process/task_queues.js:85:21)
```

Please split up `local_ip` to be able to separately specify the bind address and the external address.