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/check_queue.html.twig

@@ -0,0 +1,23 @@
+{% if nbRedisMessages is defined and nbRedisMessages > 0 %}
+    <script>
+        Materialize.toast('Messages in queue: {{ nbRedisMessages }}', 4000);
+    </script>
+{% endif %}
+
+{% if nbRabbitMessages is defined and nbRabbitMessages > 0 %}
+    <script>
+        Materialize.toast('Messages in queue: {{ nbRabbitMessages }}', 4000);
+    </script>
+{% endif %}
+
+{% if redisNotInstalled is defined and redisNotInstalled  %}
+    <div class="card-panel red darken-1 white-text">
+        {{ 'flashes.import.error.redis_enabled_not_installed'|trans|raw }}
+    </div>
+{% endif %}
+
+{% if rabbitNotInstalled is defined and rabbitNotInstalled  %}
+    <div class="card-panel red darken-1 white-text">
+        {{ 'flashes.import.error.rabbit_enabled_not_installed'|trans|raw }}
+    </div>
+{% endif %}