Expand available commands over MQTT

[StarkJohan]

This is a placeholder feature request quickly jotted down to have an issue to build upon.

What?
Add more subscription topics to make the user or home automation control more settings of the emulator.

Why?
This allows for more granular control of the emulators behaviour and opens up for further automation possibilities.

Details please
To me it would be very useful to set the lower and upper limits of the scaled SOC. With that available I can indirectly control the "AI" controller that normally has full control over my inverter. By changing the available SOC range I can charge and discharge the battery as the "AI", when not actively controlling, always aims for a certain SOC.
In a similar way I can see how max charge and discharge could also be useful to control.