* Release notes 0.26.0-rc.3 and revise bridges overview

* Fix version module and add latest release notes; update some doc menus

* Let release notes be discoverable

* Documentation master index

* Documentation index pg

* Update ops for version

* Update illustration

* Remove old illustration

* Add note for 0-rc.4

* Add section on NGRAPH_PROFILE_PASS to backend API

* rc-0.5

* Final preview 0.26 release notes

* Note changes on Sum validation

* Fix link syntax that breaks on Sphinx 3.0

* Revert file that triggers unnecessary review

* Typo fix

* PR feedback

* Consistency on section title capitalizations

* Update link

* Section title consistency