Remove pluralized report types

Report types were incorrectly pluralized for AAIB Reports.
Merge pull request #30 from alphagov/remove-aaib-report-type-pluralization

Remove pluralized report types
Bulletin report type for AAIB reports
Merge pull request #31 from alphagov/add_bulletin_report_type

Bulletin report type for AAIB reports
Display multiple values on frontend

In order to correctly send facet_values that can now possibly be
multiple items, we need to turn all the facet values into Arrays when
expanding them to fetch the label.
Merge pull request #32 from alphagov/display-multiple-values-on-frontend

Display multiple values on frontend