Split support into two pages

The kind of communications we’re getting at the moment can broadly be
broken down into:
- problems
- questions and feedback

We will need to triage problems differently, because they could
potentially be urgent/severe/emergency/P1/whatever language we use.
Questions or feedback will never be P1.

Two reasons for making the user categorise their tickets themselves:

- Outside of hours we can’t get someone out of bed in order to decide if
  a ticket is a problem or just feedback

- We can tailor the subsequent pages to whether it’s a problem or
  feedback (eg showing a link to the status page if the user is having
  a problem)

This commit let’s users make the choice with a pair of radio buttons.

It also cleans up a bunch of the tests and parameterizes them so we’re
testing the flow for both ticket types.

app/main/validators.py

@@ -35,7 +35,7 @@ class ValidGovEmail(object):
         message = (
             'Enter a central government email address.'
             ' If you think you should have access'
-            ' <a href="{}">contact us</a>').format(url_for('main.feedback'))
+            ' <a href="{}">contact us</a>').format(url_for('main.support'))
         if not is_gov_user(field.data.lower()):
             raise ValidationError(message)