introduce static configs to enable/disable web-update (and possibly more later on)

Signed-off-by: Michael Kaufmann <d00p@froxlor.org>

lib/config.inc.php

@@ -0,0 +1,8 @@
+<?php
+
+/**
+ * change the options below to either true or false
+ */
+return [
+	'enable_webupdate' => false
+];