Removed old PHP code, migrated to Python and Flask

Update .dockerignore, .env, and 503 more files...

templates/pages/_content_index.jinja

@@ -0,0 +1,7 @@
+{% extends "base_www.jinja" %}
+
+{% block main_content %}
+    {% block content_filters %}{% endblock %}
+    <hr class="subtle">
+    {% block content_listing %}{% endblock %}
+{% endblock %}