SQL: add release notes for refactor (GH6292)
This should (finally) close #6292.

WIP for now, but comments welcome. Have to add to release.rst.

@jreback Should I mark the new sql as experimental? (and if so, where should I do this?)

that looks good to me

I don't think u need to mark as experimental
what/why do u want to do that?

everything should be back compat yes?

or is some part of the API still a bit experimental?
 No, I think it should be OK. But I think you added that in the list of #6292? Only the OO api is not yet well defined, but this is also not publicly exposed in the docs or top-level namespace.
 oh ok

just delete the experimental ref
 can you merge this in (even if not 100% finished) before RC1? just want to make sure that whatsnew is pretty complete
 yes, it can certainly be merged. Will rebase now
 go for it

btw I currently have is released set to True (so it makes tags as rc1)

should I change this back to False

and then turn it back in when we actually release?

any idea ?
 merge when ready
 yep, can be merged, but then it is not included in 0.14rc1?

I am not familiar with the release process, so don't know how the setting of release to True/False works. That's something that maybe should be documented in the wiki.
 I'll leave it for now; I have been updating the release checklist (was pretty good anyhow).

This will just update the docs (which the ann points to anyhow).
 going to mail you the ANN, pls lmk any comments before I send out
