[bug 839248] Fix case of untranslated document

These don't have a parent because we are passed the en-US already.
s/request.locale/request.LANGUAGE_CODE/
[bug 846756] Add A/B test for product ordering on /products

?b returns the first two products in reverse order.
[bug 839157] l10n remaining email templates

* l10n-ifies the remaining email templates
* adds locale-aware emails_with_users_and_watches
* add rest of email templates to DOMAIN_METHODS
Refactor email sending in wiki

I created a locale-aware emails_with_users_and_watches in email_utils,
so this switches a bunch of the wiki events code to use that.
[bug 839041] Fallback to top articles when there are no search results.