Gds upgrade tags and things

There were a few bitty bits that I needed to get in here before I can tackle the new artefact edit form and subsequent tag editing.

- tags helper refactoring and cleanup of old legacy tags
- includes initial setup for airbrake.

 ***NOTE***: 

once this is merged/deployed, it's worth checking with a real signon that people can log in/out as this PR includes an update to gds-sso.