Adding three redirects for old Directgov PDFs

Approved by the content guys - Zen desk tickets:

https://govuk.zendesk.com/agent/#/tickets/509394
https://govuk.zendesk.com/agent/#/tickets/549886
Configure IPO for transition app
Add TLD generation tool
Merge pull request #571 from rjc123/newmappings

Configure monitor on transition app
Merge pull request #569 from rjc123/admin

Add TLD generation tool
Merge pull request #570 from rjc123/newsites

Configure IPO for transition app
Merge pull request #568 from alphagov/add_some_directgov_pdf_mappings

Adding three redirects for old Directgov PDFs
Merge pull request #572 from rjc123/newmappings

Add alias and revise monitor site configuration