Initialize is extended multiple times by modules. These modules
will take any number of args and hand them on:

def initialize(*)
  ...
  super
end

The original ActionController::Base#initialize however does not accept
arguments. If we extend initialize in Page::BaseController there is no
way of telling if we are dealing with such an extended controller as
```
controller.method(:initialize).arity
```
will always return -1.

We could allow seeding in all controllers that a DispatchController
might dispatch to. But that implies a lot of knowledge of the dispatcher
about its targets.

Instead we now allow defining a `seed` method on the controller that
will be called to hand over the page, group and user if it exists.