Send emails with a friendly from name

It’s nicer to have emails with a sender name, as well as the raw email
address.

Amazon SES can acheive this by using the format
```
"Sender name" <sender.name@domain.com>
```
— http://docs.aws.amazon.com/ses/latest/DeveloperGuide/email-format.html
We also have to remove all non-ASCII characters from the sender name,
because SMTP only supports 7-bit ASCII:

> A field name MUST be composed of printable US-ASCII characters (i.e.,
> characters that have values between 33 and 126, inclusive), except
> colon.

— http://www.ietf.org/rfc/rfc5322.txt

We use the service name as the sender name when:
- sending emails from the API
- sending emails from a CSV file

We use GOV.UK Notify as the sender name when:
- sending invitation emails
- sending password reset emails

app/notifications/rest.py

@@ -359,7 +359,7 @@ def send_notification(notification_type):
         send_email.apply_async((
             service_id,
             notification_id,
-            "{}@{}".format(service.email_from, current_app.config['NOTIFY_EMAIL_DOMAIN']),
+            '"{}" <{}@{}>'.format(service.name, service.email_from, current_app.config['NOTIFY_EMAIL_DOMAIN']),
             encryption.encrypt(notification),
             datetime.utcnow().strftime(DATETIME_FORMAT)
         ), queue='email')