Add support for PHP array config files

- Add new base config files
- Remove useless DIRECTORY_SEPARATOR instances

config/addon-sample.config.php

@@ -0,0 +1,12 @@
+<?php
+
+// Addon configuration
+
+// Copy this configuration file to addon.config.php and edit it if you want to configure addons, see below example for the twitter addon
+
+return [
+	'twitter' => [
+		'consumerkey' => 'localhost',
+		'consumersecret' => 'mysqlusername',
+	],
+];