make all themes have a Page class, to simplify loading

themes/lite/page.class.php

@@ -0,0 +1,12 @@
+<?php declare(strict_types=1);
+
+class Page extends BasePage
+{
+    /** @var bool  */
+    public $left_enabled = true;
+
+    public function disable_left()
+    {
+        $this->left_enabled = false;
+    }
+}