This change reduces the amount of sent data towards clients. Inventory lists that are already known to the player are skipped, saving quite some data over time.
Raises protocol version to 38 to ensure correct backwards-compatible code.
* Server: delegate mod management & config to ServerModConfiguration (rename it to ServerModManager)
* Use c++11 range based loops
* Add unittests + experimental/default mod as a test case to permit testing mod loading in future tests