Fix #308 -- Preview for email templates (#438)

* add ajax and dummy api response

* add preview <p> blocks

* finalise order_placed setup

- use <pre> for mail preview
- create dummy data in backend

* fix i18n text conversion

* create fragment template for mail preview

* support i18n in mail preview view

* apply mail fragment in all mail settings

fix mistake in input[lang=en] flag style
add dummy data for all placeholders
apply fragment template to all fields
add exclude option to fragment template

* remove migration file

* add translation mapping & fix field label

remove hardcoded field label
add transblock for translation file

* add test for mail setting preview

* fix code style in preview class

* bug fix in mail preview view

- fixed localised date values
- added locale index mapping
- added tests on multi-language event
- enhanced dummy data

src/pretix/control/urls.py

@@ -52,6 +52,7 @@ urlpatterns = [
         url(r'^settings/tickets/preview/(?P<output>[^/]+)$', event.TicketSettingsPreview.as_view(),
             name='event.settings.tickets.preview'),
         url(r'^settings/email$', event.MailSettings.as_view(), name='event.settings.mail'),
+        url(r'^settings/email/preview$', event.MailSettingsPreview.as_view(), name='event.settings.mail.preview'),
         url(r'^settings/invoice$', event.InvoiceSettings.as_view(), name='event.settings.invoice'),
         url(r'^settings/invoice/preview$', event.InvoicePreview.as_view(), name='event.settings.invoice.preview'),
         url(r'^settings/display', event.DisplaySettings.as_view(), name='event.settings.display'),