Merge pull request #499 from rjc123/zendesk

Resolve zendesk ticket to unpublish business link assets https://govuk.z...
Add an initial Environment Agency site

I used the most recent TNA crawl datetime. I had a brief look for significant
querystring parameters. There are definitely some, but I didn't want to do half
a job; better that it obviously hasn't been done.
Merge pull request #498 from alphagov/add_ea

Add an initial Environment Agency site
Resolve canonicalisation failures.