Mqtt discovery (#320)

* add mqtt discovery (compatibile with home assistant) with omg status binary sensor & bme280 sensor

* added mqtt discovery to Test_config.h for ESP32 (ESP8266 & other boards was not tested)

* include support for ESP8266 & arduino mega

* fix getting MAC for esp8266

* esp8266 fix

* make mqtt discovery functions functions more generic, readable and easy to use & extend

* make mqtt discovery functions functions more generic, readable and easy to use & extend PART 2

* remove the macro for each attribute and supposing that if there is a bme280 we expose all

config_mqttDiscovery.h

@@ -0,0 +1,32 @@
+/*
+  OpenMQTTGateway  - ESP8266 or Arduino program for home automation
+
+   Act as a wifi or ethernet gateway between your 433mhz/infrared IR signal  and a MQTT broker
+   Send and receiving command by MQTT
+
+   This files enables to set your parameter for the Home assistant mqtt Discovery
+
+    Copyright: (c) Rafal Herok
+
+    This file is part of OpenMQTTGateway.
+
+    OpenMQTTGateway is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenMQTTGateway is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+#define discovery_Topic "homeassistant"
+#define omgStatus //uncomment to create OMG status sensor
+#define discBme280 //uncomment to enable bme280 sensors
+
+#define DEVICENAME "OpenMQTTGateway " Gateway_Name
+#define DEVICEMANUFACTURER "AnimaVitis"