Legacy bridge energy monitoring

[andersevenrud]

After #15 (PR: #16) lands, this needs to be looked into as monitoring information about power on the base device node will be disabled.

The old API responds with:

{
    "kW": 0.0,
    "kWh": 0.0
}

However, I don't have access to see what this actually means. Is kW the meter or the current draw, or is kWh ?

So currently, metering is disabled.

Also, the X bridge comes with date based values as well, so the models and sensors needs to be changed to reflect this when this has been figured out.

Another thing; is the /energy/nodes available ?!