[components] refactor main template header: make it much more flexible by using CtxComponent * rename userlink class (not private) with somewhat bw compat * make some cosmetic adjustements on log-in/registration components * update to component api, though this may breaks some sub-classes (for application customizing the breadcrumbs component for instance)

.. -*- coding: utf-8 -*-
 
Dernières modifications
-----------------------

* la table des `derniers changements`_ fournit un exemple d'utilisation de RQL
  pour récupérer les derniers changements ayant eu lieu sur ce site.

.. _`derniers changements`: view?rql=Any+M%2CX+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30