[RLS] 6.0

[wsbrenk]

** Release Process:**

• [x] create release branch
• [x] update release note in HO (up to date before BETA)
• [x] terminate DEV Q&A, create 1st BETA
• [x] announce it both to translators and on HT forum
• [x] finish release_notes and HT forum announcement @DavidatorusF
• [x] terminate BETA Q&A
• [x] update release note in HO (up to date before STABLE)
• [x] update stable branch
• [x] release stable inc. artefacts publication
• [x] update latest Release information on ReadMe
• [x] update HO/docs/latest*.html and verify the presence of release_notes(*).md in the master branch required by the HO3 update
• [x] publish HT forum announcement
• [ ] create ticket for next RLS
• [x] append release_notes to changelog