* factoring of the publishing function
* integration of json publishing to MQTT
* receiving and transcode json messages from mqtt
* replace the TRACE runtime condition by a buildtime one so as to decrease program size
* remove retainFlag parameter not necessary for the moment
* Increase the scope of tests for arduino mega and esp32
* Update arduinojson library to 5.13.3
* add macros to choose between simple or json publishing or both
* differentiate build test for ATmega2560
* correct wrong sprintf definition
* change IDE version for continuous integration
* let default warning level in arduino ide
* correct pins for ESP32
* reorganize user_config
with the last version of ESP32 arduino env it is not possible to compile on ESP32, we get "missing gatt_api.h" ERROR. So as to avoid that we need to use the last version of the nkolban library for BLE 0.4.16
Johno Crawford