Hass discovery improvments (#512)

Rename set commands to config
correct json buffer size and gateway name
replace state to cmd
replace set by config
add restart and erase command
add unicity to gateway command switches
BLE devices shouldn't be child of the gateway
make the BTtoMQTT topic consistent with other definitions

test/Test_config.h

@@ -176,6 +176,6 @@ char gateway_name[parameters_size * 2] = Gateway_Name;
 #endif
 #define TimeBetweenReadingSYS 120000 // time between system readings (like memory)
 #define subjectSYStoMQTT  "/SYStoMQTT"
-#define subjectMQTTtoSYSset "/commands/MQTTtoSYS/set"
+#define subjectMQTTtoSYSset "/commands/MQTTtoSYS/config"
 
 #endif