Add extra fields to AAIB Reports

This adds aircraft_type, registration and location to AAIB Reports
Merge pull request #185 from alphagov/add-extra-fields-to-aaib

Add extra fields to AAIB Reports
Fix aircraft_type typo in indexable_formatter
Merge pull request #189 from alphagov/fix-aircraft-type-typo

Fix aircraft_type typo in indexable_formatter