Split paragraph in translation
Inject wallabag_url for image in HTML template
Remove username & password from config_dev.yml (null are already the default value)
Symfony use a different class when in dev mode and prod mode.
Prod loads `Symfony\Bundle\FrameworkBundle\Translation\Translator`.
Dev loads `Symfony\Component\Translation\DataCollectorTranslator` to gather information for the debug bar.
Fix#1585