fix #728 check if thumbExtractor is supported

remove fileReader its not needed

fix unit tests

fix typo

remove unecessary message

lib/Alchemy/Phrasea/Controller/Prod/Language.php

@@ -98,6 +98,7 @@ class Language implements ControllerProviderInterface
                 $out['errorAjaxRequest'] = _('An error occured, please retry');
                 $out['fileBeingDownloaded'] = _('Some files are being downloaded');
                 $out['warning'] = _('Attention');
+                $out['browserFeatureSupport'] = _('This feature is not supported by your browser');
 
                 $Serializer = $app['Core']['Serializer'];