Reorganise templates for API keys page

This adds another layer of folder structure to the templates to match
the new URLs, which have another layer of hierarchy.

app/templates/views/api/keys/create.html

@@ -0,0 +1,22 @@
+{% extends "withnav_template.html" %}
+{% from "components/page-footer.html" import page_footer %}
+{% from "components/textbox.html" import textbox %}
+{% from "components/radios.html" import radios %}
+
+{% block page_title %}
+  Add a new API key – GOV.UK Notify
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  <h1 class="heading-large">
+    Create an API key
+  </h1>
+
+  <form method="post">
+    {{ radios(form.key_type) }}
+    {{ textbox(form.key_name, label='Name for this key') }}
+    {{ page_footer('Continue') }}
+  </form>
+
+{% endblock %}