Add index view to 'simple' example, with an explanation and a backlink.

examples/simple/templates/admin/index.html

+{% extends 'admin/master.html' %}
+{% block body %}
+{{ super() }}
+<div class="row-fluid">
+    <h1>Flask-Admin example</h1>
+    <p class="lead">
+        Simple admin views, not related to models.
+    </p>
+    <p>
+        This example shows how to add your own views to the admin interface. The views do not have to be associated
+        to any of your models, and you can fill them with whatever content you want.
+    </p>
+    <p>
+        By adding custom views to the admin interface, they become accessible through the <em>navbar</em> at the top.
+    </p>
+    <a class="btn btn-primary" href="/"><i class="icon-arrow-left icon-white"></i> Back</a>
+</div>
+{% endblock body %}
\ No newline at end of file