Member callback (char *topic, byte *payload, unsigned int length): Change global implementation of callback. Maybe with static?
File CommunicationConfiguration.h: Switch Password to .ini file
https://community.platformio.org/t/how-to-specify-ota-upload-password-outside-platformio-ini/3588
http://docs.platformio.org/en/latest/envvars.html#building
File MQTTCommunication.h: Split the Code into two Repos: SmartFactory_Communication-Sortic
and SmartFactory_MQTTCommunication-Basis to simplify modular use.
File myMQTT.h: Add a function "unsubscirbeAll" which unsubscribes from all subscirbed topics. Hence you need to track all your subscribed topcis in an array.