Split rtc time adjustment into a sperate sketch

[ValentinTT]

The arduino can be restarted, so if the rtc module is adjusted within the setup function using the compilation time, it can leads to a miscoordination between differents arduinos because of the sleeping mode. So the rtc should be configurated an a different sketch before connect it to the whole system. Even more, in the future it could be configurated using the sim800L time or so.