Added some setNouns

I didn't make them up:

* [Lie algebra](https://en.wikipedia.org/wiki/Lie_algebra)
* [Dynkin system](https://en.wikipedia.org/wiki/Dynkin_system)
* [sigma-algebra](https://en.wikipedia.org/wiki/Sigma-algebra)
* [ultrafilter](https://en.wikipedia.org/wiki/Ultrafilter)