rename .html templates to .jinja2 for more consistency

templates/viewold.html

@@ -1,13 +0,0 @@
-{% extends "view.html" %}
-
-{% block meta %}
-<meta name="robots" content="noindex,nofollow" />
-{% endblock %}
-
-{% block history_nav %}
-<div class="history-nav">
-  <p>{{ T('old-revision-notice') }}
-    <time datetime="{{ rev.pub_date.isoformat() }}">{{ rev.pub_date.strftime('%B %-d, %Y at %H:%M:%S') }}</time>
-  (ID #{{ rev.id }}). <a href="{{ p.get_url() }}">Show latest</a></p>
-</div>
-{% endblock %}