[sources] Simplify source's init method
Only call it when enabled instead of giving a boolean flag indicating whether it
is or not (which were not correctly considered).
.. _login_module:
:mod:`cubicweb.pyramid.login`
-----------------------------
.. automodule:: cubicweb.pyramid.login
.. autofunction:: includeme
Views
-----
.. autofunction:: login_form
.. autofunction:: login_password_login
.. autofunction:: login_already_loggedin