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/templates/kfetcms/block_menu.html

@@ -0,0 +1,11 @@
+{% load static %}
+
+{% if pressions %}
+  {% include "kfetcms/block_menu_category.html" with title="Pressions du moment" articles=pressions class="carte-inverted" %}
+{% endif %}
+
+{% regroup articles by category as categories %}
+
+{% for category in categories %}
+  {% include "kfetcms/block_menu_category.html" with title=category.grouper.name articles=category.list %}
+{% endfor %}