Translatable Booking Button Labels

Bilingual sites need every visitor-facing string in every language, and the booking button is one of the most visible strings on an event page. The Book Button Label on events and event instances is now a translated field, editable per language in the admin and rendered in the visitor's language on the site. Existing labels are carried into the default language, so nothing needs re-entering.

Clearer Booking app fields

The Booking app adds a booking group to both the event and the event instance edit views, and until now the two looked identical. The fields are now labelled to show that the URL points at an external ticketing site, which level you are editing, and which value wins when both the event and an instance have one set.