Add links to user survey to emails, front page and confirmation pages

Use the cross sell function to put an 'advert' for the survey on the
various confirmation pages
Create new alert email templates for fixmystreet co-brand so we can
include the survey link on those alone
All as one commit for ease of reverting when the survey is done.
Make alert_type.t test more robust.

Put alerts in default cobrand, so changes to other cobrand email
templates don't affect the test; and clean up at the end of the
test so that it can be rerun without issue.
Explanatory text/link on /my with no reports

Usually you won't get to "Your Reports" page without any
content (reports or updates) but it's possible to do so,
as we just discovered in a client meeting, logging into
that page, and arriving on a screen of blank content with
no guidance.  This patch shows some text and a link to
create a new report, if there aren't any problems/updates.

Fixes #671
Merge branch 'issues/671-guidance-on-no-reports' into hart