Add pages for ‘service settings’ flow

Adds the pages and wires them together, so that it’s possible to click
through them.

The wording is not quite English, but attempts to be an rough description of
what the consequences are for each of the four actions.

app/templates/views/service-settings/delete.html

@@ -0,0 +1,22 @@
+{% extends "withnav_template.html" %}
+{% from "components/submit-form.html" import submit_form %}
+
+{% block page_title %}
+  GOV.UK Notify | Service settings
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  <h1 class="heading-xlarge">Delete this service</h1>
+
+  <p>
+    All will be lost.
+  </p>
+
+  <form method="post">
+    {{ submit_form('Delete', destructive=True) }}
+  </form>
+
+  <p><a href="{{ url_for('.service_settings') }}">Back to service settings</a></p>
+
+{% endblock %}