Renamed the ChainLogger to LoggerChain

This is now consistent with the naming used in the ORM.

lib/Doctrine/DBAL/Logging/ChainLogger.php → lib/Doctrine/DBAL/Logging/LoggerChain.php

@@ -27,7 +27,7 @@ namespace Doctrine\DBAL\Logging;
  * @since   2.2
  * @author  Christophe Coevoet <stof@notk.org>
  */
-class ChainLogger implements SQLLogger
+class LoggerChain implements SQLLogger
 {
     private $loggers = array();