chain argument of utils functions
We have a chain argument in the following utils functions for creating bodies:
Documentation of all these functions refer to utils.sphere doc for the meaning of that attribute, but there is actually no chain argument therein.
Usage of that chain attribute is never illustrated in the examples, according to find . -type f | xargs grep chain # from examples folder.
Such an attribute was introduced for the facet case in da0d218b, when none of the 3 other functions existed.
At the moment, I do not know what this chain body attribute stands for (outside of Body.chain which does not help me much -- I have not found yet where this is used in the C++) and wonder whether it makes sense to have it in these 4 utils functions.