Added XmlWriter to easily generate XMLs 

e.g
        $xmlWriter = new XmlWriter();
        $xmlWriter->setRootElementName('RESPONSE')->setConfig(array('success' => 'yes'))->displayXML();

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@5461 1f8fe7d8-47f0-464c-8d0a-336f4953ab05