backport simple blog index page from rev a7375a677ec43f581eeae1b569f1ccd1885d5198

pages/blog/index.html

+{% extends "global/layout.html" %}
+{% block title %}Blog Index{% endblock %}
+{% block content %}
+<p>Some descriptive text.</p>
+<ul class="infolist">
+{% for entry in entries -%}
+  <li><a href="{{ url_for('blog_entry', slug=entry) }}">{{ entry }}</a></li>
+{%- endfor %}
+</ul>
+{% endblock %}