Export reports as CSV on /dashboard

Provide a button to download the details and text of reports
at the second "Look up" button on /dashboard.

Provides acknowledged, fixed, closed dates by parsing updates.

Fixes #692 (and mysociety/FixMyStreet-Commercial#399)

Email is not shown, and name honours anonymous flag: as /dashboard
is accessible to people who are from_body (who still do not see
anon-users name and email in the FMS web app.)

A basic test is provided as per Zurich's similar report.