* 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

* Fix ops, cleanup ToC, add latest illustrations

* PR feedback

* Update ngtf bridge doc for generic versioning

* Many improvements, including previous group-based edits

- New section for docs on extra-experimental project-based features
- Team-based edits from PR 2994 added
- Reorganize GSG sections to be cleaner for getting started
- Fix link style warning generated by broadcast.hpp

* Update README with correct ngraph-bridge link on tf repo

* Fix comment so warning not generated on broadcasting op

* Add latest doc changes to ReleaseNotes

* Fix wording suggestion on PR review

* Update HE Transformer experimental backend

* Add instructions for building the NGRAPH_PLAIDML backend, ref on latest ToC

* Fix typo

* Reword paragraph to reference ngraph-plaidml build instruction page

* PR review suggestions added

Update template for release notes and CHANGELOG with latest few summaries from ngraph releases repo (#2696)

* Update Release Notes for Github summaries, incorporate feedback from doc review, fix typos, etc

* Fix links

* Rename RCs on template

* PR reviews

* Remove trailing spaces and add clarification on Python API example

* Fix typo

* [ONNX] Add documentation

* Update documentation contributor's instructions

* Cleaner API doc reference for compile call

* Add a useful table for nGraph namespaces

* Remove layout namespace

* Show exploding kernel problem on illustration like IEEE preso

* Add new Introduction section based on IEEE presentation and illustrations

* WIP changes to doc navigation

* Update illustrations

* Cleaner ToC

* Minor fixes to the theme and removing useless bower files

* Better captions

* Revise intro

* Latest

* Make framework support section be its own section

* More updates to backend support section and add a new cpp api

* add changes to section

* Update intro with better detail

* Rework intro with better detail on motivation

* Editing

* Update README with new contrib guide filename

* Add the illustration referred to RE MobileNet group convolution fusion

* Fix off-by-a-line emph on code description

* Fix off-by-a-line emph on code description