Add a modbus device IP override to the launch arguments

[tjhowse]

The IP addresses in the example YAMLs are not useful to the majority of people. It would make it easier for people to use the bundled YAMLs directly if the IP address of the modbus device could be overridden in a launch argument.

[woifes]

I was about to write a similar suggestion. I am just planing the deployment fo multiple instances of this service. The devices have identical modbus registers but ofc different IP addresses. If the modbus IP is a launch argument, I can map the same register definiton into every container via docker compose but override the IP in the compose file for each instance.

An alternative would be to allow the register definiton in a separate file.