Merge Changelog.md, Authors, UPGRADE.md into -dev after releasing 1.2.2

Hello,

we need to merge Changelog.md, Authors, UPGRADE.md into -dev after releasing 1.2.2

Cheers

created branch 5877-merge-changelog-md-authors-upgrade-md-into-dev-after-releasing-1-2-2

By bmortier on 2018-08-19T11:43:41 (imported from GitLab)

mentioned in merge request !375

By bmortier on 2018-08-19T11:43:42 (imported from GitLab)

closed via merge request !375

By bmortier on 2018-08-19T12:02:44 (imported from GitLab)

mentioned in commit fadfbbbe

By bmortier on 2018-08-19T12:02:44 (imported from GitLab)

mentioned in commit 01b6002e

By bmortier on 2018-08-19T12:03:12 (imported from GitLab)

mentioned in merge request !376

By bmortier on 2018-08-19T12:03:47 (imported from GitLab)