Added Optional configuration file (#338)

* Added optional configuration file loading

* First commit of optional configuration file

This file is OPTIONAL.
If this file is not present in your webserver, tinyfilemanager will works with its internal configuration.

* removed define

define is not a configuration

tinyfilemanager.php

@@ -137,6 +137,12 @@ $ip_blacklist = array(
     '::'            // non-routable meta ipv6
 );
 
+// Load configuration file, if present
+$config_file = 'h3k_config.php';
+if (is_readable($config_file)) {
+    include($config_file);
+}
+
 // --- EDIT BELOW CAREFULLY OR DO NOT EDIT AT ALL ---
 
 // Set the max upload file size