Retry merge folder rename if it doesn't work for the first time after one second.
Improved Depth of Field Effect

Depth of field now works as it should, with objects being blurred
proportional to their distance from the focal point of the camera. The
blur is also gradual to be similar to how our eyes work.
Make it possible to become op on a headless server.

The config file contains now a one time authorization key which can be used
to get op rights on a headdless server.
Merge PR #1427 by @flo - fixes #1403 (save game crash)
Merge PR #1429 by @IWhoI - depth of field
Add CommandParameter annotation on a new command
Update readme with new multiplayer section + new credits entry, and fix up gradlew start to not overwrite config.cfg
Made the subscribe method not be overloaded by renaming them.
For future use: Record the changes of entities between saves.
Seperated the recursive entity deactivation from the serialization
of the same entities for saving.
Use the recorded delta to update a entity manager private to
the storage manager and it's helper classes.

The copy gets updated and read off the main thread and makes it possible
to do the entity serialization off the main thread.CAll onEntityDeactivated
UNTESTED: Save entities off the main thread.
Made the saving more verbose for debugging.