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

system/compat/config.php

@@ -45,6 +45,7 @@ $deprecatedConfig = [
 	'signature_type',
 	'signature_cache_time',
 	'signature_browser_cache',
+	'gifts_system',
 ];
 
 foreach ($deprecatedConfig as $key => $value) {