New hierachy for stackname credentials
New hierachy for stackname credentials

This would allow overwriting credentials for a specific stack. This may
be required for things like Jenkins, which generates tokens based upon
the instance it's running on.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet