We have a pretty though decision to make here. If we do a deep merge, we can extend deep settings without having to re-write them, but we can't really unset definitions. If we do a superficial merge, we can unset deep settings (but not superficial ones), but will have to repeat deep level definitions. Looking at the current files, there is no setting that goes below one level deep.

If we continue using deep merging, which I tend to like more, we can still assign any property to ```null``` so we could handle this as equal to undefined (which probably already works).

**P.s.: to change from deep merge to superficial merge would mean to only change the ```mege``` method to ```assign``` (or ```extend```, which behave the same).**