Completely integrate wepack in django

* Migrate alpine
* Migrate jquery and jquery-ui
* Migrate shorten
* Add babel for javascript
* Introduce staticfiles django app
* Only bundle -index.js files in static/webpack
* Unify scss and webpack generated files
* Convert scss calls to static
* Add --clear-generated option to collectstatic
* Fix docs warnings

com/templates/com/screen_slideshow.jinja

@@ -2,7 +2,7 @@
 <html lang="fr">
   <head>
     <title>{% trans %}Slideshow{% endtrans %}</title>
-    <link href="{{ scss('com/css/slideshow.scss') }}" rel="stylesheet" type="text/css" />
+    <link href="{{ static('com/css/slideshow.scss') }}" rel="stylesheet" type="text/css" />
   </head>
   <body>
     <div id="slideshow">