Hard coded links in header for UKVI

Relates to https://www.pivotaltracker.com/story/show/67911210

This is a temporary solution and should be refactored if more orgs
request this feature. Ideally we should move it out to an actual attr
instead of having a big messy hash in the org model.
Merge pull request #1361 from alphagov/ukvi-top-tasks

Hard coded links in header for UKVI