Add Roles and Permission models so that only admins can access /admin

app/templates/main/admin.html.j2

@@ -0,0 +1,12 @@
+{% extends "base.html.j2" %}
+
+{% block page_content %}
+<h1>Administration tools</h1>
+<div class="col s12">
+  <div class="card large">
+    <div class="card-content">
+      <span class="card-title">User list</span>
+    </div>
+  </div>
+</div>
+{% endblock %}