Cosmetic: Remove unused imports
Add autoescape extension to Jinja config

We need this for email templates.
Add send_messages convenience function to email_utils
[bug 846386] l10n the kb email templates

* overhaul code to support setting the right locale for each user
  for each email sent
* convert kb email templates from Django to Jinja2
Add autoescape wrappers to users app email templates

The emails are text-based, so this prevents html escaping which makes
it difficult to read them.
Add autoescape wrapper to questions email templates

Emails are text-based, so it's weird to be html escaping them.