Improvements for K-Fêt CMS.

K-Fêt - Wagtail
- Page content becomes a StreamField.
- GroupTeam snippet becomes a block for stream field.
- Navigation menu moved becomes a "flatmenu", preventing possible future conflicts.
- Page layout can be modified in wagtail admin.

K-Fêt
- Add shorthands for ukf account balance/article price.
- Cleaning stylesheets and templates.

kfet/cms/apps.py

@@ -5,3 +5,6 @@ class KFetCMSAppConfig(AppConfig):
     name = 'kfet.cms'
     label = 'kfetcms'
     verbose_name = 'CMS K-Fêt'
+
+    def ready(self):
+        from . import hooks