Make speech translatable

This is now as simple as ensuring that `Speech#translatable?` returns true.
The tests that ensure the controller is hooked up correctly are all in
`Admin::GenericEditionsController::TranslationTest`.
Make case study translatable

This is now as simple as ensuring that `CaseStudy#translatable?` returns true.
The tests that ensure the controller is hooked up correctly are all in
`Admin::GenericEditionsController::TranslationTest`.