[FIX] *: do not use groups when extending an asset bundle

Using groups when declaring an extension of an asset bundle leads to a
different generated asset bundle according to the user's group. This
is not something we want because a dynamic asset bundle's content
means that it could (and it does) trigger unwanted cache invalidation.

website_event, website_blog, website_forum and website_sale add
functions to `website.contentMenu`. These functions are bound to
server side qweb nodes protected by groups. We can always add the
functions; if a user tries to use the routes he should receive a
traceback because of lack of access rules

website_blog adds a `website_blog.editor` module, but is guarded by
the presence of a node in the DOM. We use the same logic to guard the
module added by website_sale with the `.js_sale` node.

website_gengo is working as expected.