mqtt refactoring, change version to 1.4.0-rc.1

* added MqttWriter
* added MqttWiFiClient (modified WiFiClient for esp8266)
* adaptation HomeAssistantHelper for MqttWriter
* adaptation HaHelper for new HomeAssistantHelper

platformio.ini

@@ -32,7 +32,7 @@ build_flags =
 	-D USE_TELNET=1
 upload_speed = 921600
 monitor_speed = 115200
-version = 1.4.0
+version = 1.4.0-rc.1
 
 ; Defaults
 [esp8266_defaults]