Changelog for 1.9.0 (#7664)

* Move 1.8 changelog to docs/

* Add EOL notices for 0.9-1.7

* Add changelog for 1.8.7 stable

* Prepare changelog for 1.9.0 beta

* Update changelog for 1.9 beta

* Update changelog for 1.9 beta

* Fix typos in changelog

* Add changelog for 1.7.13

* Update CHANGELOGs for 1.9, 1.8, 1.7

* Update readme for 1.9

* Update CHANGELOG for 1.9