make ON OFF actuator more flexible (#481)

* make ON OFF actuator more flexible

enable to choose the pin when sending the MQTT command

* add on off environment example

docs/use/actuators.md

@@ -3,13 +3,21 @@
 This module enables to actuate things by giving to a PIN a HIGH or LOW value corresponding to an MQTT topic.
 Example usage: Connect a transistor to power a relay, connect a led...
 
-So as to pilot the pin use the following commands:
+So as to pilot the pin use the following commands with [simple receiving](../upload/pio.md#api):
 
 OFF command:
-`mosquitto_pub -t home/OpenMQTTGateway_MEGA/commands/MQTTtoONOFF -m OFF`
+`mosquitto_pub -t home/OpenMQTTGateway_MEGA/commands/MQTTtoONOFF/setOFF -m 15`
 
 ON command
-`mosquitto_pub -t home/OpenMQTTGateway_MEGA/commands/MQTTtoONOFF -m ON`
+`mosquitto_pub -t home/OpenMQTTGateway_MEGA/commands/MQTTtoONOFF/setON -m 15`
+
+or with [json receiving](../upload/pio.md#api)
+
+OFF command:
+`mosquitto_pub -t home/OpenMQTTGateway_MEGA/commands/MQTTtoONOFF -m '{"pin":15,"state":0}'`
+
+ON command
+`mosquitto_pub -t home/OpenMQTTGateway_MEGA/commands/MQTTtoONOFF -m '{"pin":15,"state":1}'`
 
 ## FASTLED