Move switch service out of black header

Also following the pattern work that Tim and Stephen have done.

app/templates/withnav_template.html

@@ -1,6 +1,12 @@
 {% extends "admin_template.html" %}
 
 {% block fullwidth_content %}
+  <div class="navigation-service">
+    <h2 class="navigation-service-name">
+      {{ current_service.name }}
+    </h2>
+    <a href="{{ url_for('main.choose_service') }}" class="navigation-service-switch">Switch service</a>
+  </div>
   <div class="grid-row">
     <div class="column-one-third">
       {% include "main_nav.html" %}