merged branch everzet/dbal-fix (PR #2635)

Commits
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24dcd0f [DoctrineBundle] added missing default parameters, needed to setup and use DBAL without ORM

Discussion
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[DoctrineBundle] added missing default parameters for DBAL

Without this change, user can't use DBAL without ORM. When user configures only DBAL - he'll get:

    [Symfony\Component\DependencyInjection\Exception\ParameterNotFoundException]
    The service "doctrine" has a dependency on a non-existent parameter "doctrine.entity_managers".

src/Symfony/Bundle/DoctrineBundle/Resources/config/dbal.xml

@@ -14,6 +14,8 @@
         <parameter key="doctrine.dbal.events.mysql_session_init.class">Doctrine\DBAL\Event\Listeners\MysqlSessionInit</parameter>
         <parameter key="doctrine.dbal.events.oracle_session_init.class">Doctrine\DBAL\Event\Listeners\OracleSessionInit</parameter>
         <parameter key="doctrine.class">Symfony\Bundle\DoctrineBundle\Registry</parameter>
+        <parameter key="doctrine.entity_managers" type="collection"></parameter>
+        <parameter key="doctrine.default_entity_manager"></parameter>
     </parameters>
 
     <services>