add a query param to analytics page to track report creation

To do this we need to add a reporter_seen variable to the problem table
so we can track if this is the first time the reporter has seen the
report when they view the report page when creating a page logged in.

If it is then we set the reporter_seen flag and tweak the page that
GA sends to indicate a report has been created.

If the user is confirming by email we set the flag and tweak the
analytics page on the confirm page in case they don't click through to
the report page.

Also remove event code on report creation as it turns out events
are not at all useful for funnel analysis.
create westminster council so report_new test can run standalone

The test relies on a body for westminster council existing which is
crated in an earlier test if you run the whole test suite. However it's
not present if you run only this test against an empty database so add
it to the list of created bodies.