Move to Symfony Flex

The structure changed completely.
Bundles are gone. Everything is flatten in the folder `src`.
I separated import & api controllers to avoid _pollution_ in the main controller folder.

templates/Import/wallabagV2.html.twig

@@ -0,0 +1,3 @@
+{% extends "Import/wallabagV1.html.twig" %}
+
+{% block title %}{{ 'import.wallabag_v2.page_title'|trans }}{% endblock %}