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.

config/packages/nelmio_api_doc.yaml

@@ -0,0 +1,17 @@
+nelmio_api_doc:
+    areas: # to filter documented areas
+        path_patterns:
+            - ^/api(?!/doc$) # Accepts routes under /api except /api/doc
+    documentation:
+        info:
+            title: wallabag API documentation
+            description: This is the API documentation of wallabag
+            version: 2.x
+        securityDefinitions:
+            Bearer:
+                type: apiKey
+                description: 'Value: Bearer {jwt}'
+                name: Authorization
+                in: header
+        security:
+            - Bearer: []