3262: re-add Rickys changes from other repo!

3262: better md headings for cards + new dedicated Slack channel "#releases" for releases

3262: check_release.md now produces text release notes for checking, release_notes.sh sends md output to Slack

3262: added timestamp and build number

3262: removed unnecessary gems

3262: some formatting changes + security uplift of gems to shut up dependabot

3262: better wiring for version_uri

3262: slack integration, ruby uplift, more trello headings

0: added "DEPLOY TO QA" to untested cards list

0: doco!

1985: re-enabled release checking scripts

1985: added branch to release notes and check release scripts

0: Disabled check release and release notes

0: Don't share bundle dir between builds as it causes some odd errors

0: Version passed in as arg