Document generic parameters of KdTree

[Imberflur]

KdTree has several parameters and it isn't immediately apparent what they all are. IMO, further documentation here would be very helpful (unless I missed some existing documentation!).

In particular for the parameter B, I ended up looking into the changelog and the implementation to figure out that this is the leaf node bucket size. Beyond what parameters like this are, any guidance on how they might affect performance would also be nice.

Other parameters are easier to infer due to their usage in methods and/or the trait requirements on them, but I could see some explicit documentation for them also being useful!

[sdd]

Hi - thanks for raising as an issue. I could have sworn that I'd documented these somewhere, but even if I have, the fact that I can't find them within a few seconds of looking shows that you're right, they should be better documented. Will fix!