Unified documentation in Ostats()

[qdread]

Right now some useful documentation is spread around the different functions. But really the users will not be expected to call the internal functions. Instead they will just call Ostats(). So we should move any useful documentation to Ostats(). One example would be an explanation of how the input data should be formatted, for normal and circular data types

[qdread]

We need to check the documentation on older deprecated versions of pairwise_overlap() to incorporate in the documentation of Ostats(). Then we can change pairwise_overlap() to @noRd instead of @export.

[qdread]

@isafluck @yyue-r (Arya I didn't know whether you are still interested in working on this, feel free to ignore if not!)

Again I really appreciate all the work you did on the documentation. I think it will be easier for users if we consolidate the documentation so basically all of it is shown when the user types ?Ostats. Then we can keep the other functions as internal ones that the users will never "see."

In order to speed the code up, I took almost all the code out of pairwise_overlap() and put it in a different function called trait_density(). So there is not any documentation anymore in that function. But it is still preserved in the commit history here. So if we want to use any of that text, we can pull it out of that old version.

[qdread]

I think this is all resolved well enough by b6b1e25