Highlight Jenkins release stages more clearly
Highlight Jenkins release stages more clearly

- Add extra master branch check. This is redundant, but it stops the
  release tag and deployment stages from being logged confusingly on
  branch builds.
- Wrap Integration deployment in a stage, because this is no longer done
  by the govuk Jenkins helper.

alphagov/collections,alphagov/collections,alphagov/collections,alphagov/collections