[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)

.. winclude:: search_sample_queries

You can as well type complex queries using the RQL_ query language, 
used every where to build dynamic pages of this site.

You can use one of the following prefixes to specify which kind of search you
want: 

* `rql` : RQL query
* `text` : full text search

.. _RQL: doc/tut_rql