Update changelog

- Add all PRs/issues to CHANGELOG.md
- Add gitattributes merge=union for CHANGELOG.md

    This should avoid most merge conflicts

- Try merge=union for release notes
- Remove dupes from changelog
- Update credits and add chroot to releasenotes
- Remove bad releasenotes info

    As a result of porting to master there were extra bits of information
    that got in before the actual changes. These have been removed.

Author: waynew

Diff for: .gitattributes

@@ -0,0 +1,2 @@
+CHANGELOG.md merge=union
+docs/topics/release/* merge=union