Add Discontinued investigation MAIB report type

Ticket:
https://trello.com/c/hlULXxFi/447-add-report-type-for-maib-discontinued-investigation
Merge pull request #97 from alphagov/add-discontinued-investigation-for-maib

Add Discontinued investigation MAIB report type
Use a different title for signup pages

If a different title for signup pages is present in the metadata hash
use that instead.
MSAs signup page has a different title

Based on the work in the previous commit, add a different title for the
Drug & Device Alerts finder.
Change Drug safety update to titlecase

Ticket:
https://trello.com/c/noCFefAX/412-copy-change-finder-drug-safety-update
Merge pull request #99 from alphagov/title-dsu

Change Drug safety update to titlecase
Merge pull request #98 from alphagov/different-title-for-signup-pages

Different title for signup pages