Tagging UKVI content with Specialist Sectors

These Specialist Sectors should match up with
https://github.com/alphagov/panopticon/pull/130 in Panopticon.

Second half of https://www.pivotaltracker.com/story/show/65891232
Merge pull request #1277 from alphagov/tag-ukvi-content-with-specialist-sectors

Tagging UKVI content with Specialist Sectors

https://www.pivotaltracker.com/story/show/65891232