Merge 6.0 docs from master to stable/6.0 branch

All commits squashed into one due to gerrit refusing some commits in the
cherry-picked series and to simplify the final merge.

This commit brings stable/6.0 in sync with the master branch commit
6309b56bf05742db34a50536bc66e376f432fa23.

Change-Id: Id47cb5f6e6dc3264328ee473b416a848e6b96eec