Support for the new mqtt_json component

[JohanLeirnes]

The updated mqtt_json component now supports a white value and color_temp.

That could make this component work as one less component, aka adding W1 to be controlled by the white value.

Another idea is that both W1 and W2 could be connected to white value but you could connect W1 to warm white leds and W2 to cold white leds and as such make use of the color temperature part of the mqtt_json by mixing the two leds to different color_temp levels.

Just and idea i had.