Fix for symfony 4 templates

[lsv]

Possible fix for templates in symfony 4

Fixes #168

[Nyholm]

Thank you. This is related to https://github.com/php-translation/symfony-bundle/pull/142/files

Do one really need the extra config in twig?

[lsv]

The problem is in the {% extends %}
And by changing it to {% extends "@Translation:WebUI:base.html.twig" %} you get this error

Malformed namespaced template name "@Translation:WebUI:base.html.twig" (expecting "@namespace/template_name")

By changing it to {% extends "@Translation/WebUI/base.html.twig" %} it actually seems to work.

I will update the PR

[Nyholm]

Thanks!