Order Fatality Notices by first published date

Order the Fatality Notices by first published date instead of last
updated date. Change the test to ensure order remains when a Fatality
Notice is updated.
Change first published and updated dates

Change first published and updated dates so these are realistic
Merge pull request #1884 from alphagov/order-fatality-notices-by-first-published-date

Order Fatality Notices by first published date