Begin abstracting
Start speccing out API for preview data
Add preview API in backend. Need way to get of-course URL.
Merge branch 'develop' of github.com:unikent/programmes-plant into feature/add-preview-api-outputs
Handle empty secondary subject.
Make global & immutable settings save blanks correctly (needs a refactor really)
Add place to store front end URL.
Add front end url from config
Fix create programme bug.
Actually fix the bug mentioned before (missed this part of commit)
Fix bugs with preview output in API.
Add preview to "current" revision. + stabalise some features
Arrange preview button better.
Set preview expire time to 4 weeks.
Merge pull request #232 from unikent/feature/add-preview-api-outputs

Add preview feature to backend