Add BIND9 configuration for gitchangelog

Add BIND9 configuration for gitchangelog

The configuration has been crafted to cater for BIND9 needs:
- Define actions that have an equivalent section in existing Release
  Notes
- Assume the commits that have the necessary changelog makrup are merge
  commits from GitLab and transform them into messages and proper links
- Put the resulting changelog into the proper place in
  doc/arm/changelog.rst
- Have a separate configuration for changelog and release notes. Both of
  these should be generated from the `git log`, with release notes being
  subject to more scrutiny and further editing