Move rendering into private templates

Add an explicit template renderer with HTML views and partials for the app, bootstrap, package, and catalog pages. Move shared reporting setup into config/reporting.php and relocate stylesheet assets under css/.

private/views/partials/header-language.html

@@ -0,0 +1,9 @@
+<form class="header-language-form" method="get" action="{{language_action}}">
+{{{hidden_inputs_html}}}
+<label>
+{{language_label}}
+<select name="lang" onchange="this.form.submit()">
+{{{language_options_html}}}
+</select>
+</label>
+</form>