Save config.php in Settings

Egg and hen problem solved :)
* Test database connection on save settings -> prevents from making website unusable if connection is wrong
* Test server_path -> same
There is no config.php anymore, just config.local.php, which can be edited manually and also from admin panel

login.php

@@ -1,7 +1,5 @@
 <?php
 require_once 'common.php';
-require_once 'config.php';
-require_once 'config.local.php';
 require_once SYSTEM . 'functions.php';
 require_once SYSTEM . 'init.php';
 require_once SYSTEM . 'status.php';