[schema] Let RQLConstraint inherit from BaseRQLConstraint instead of RQLVocabularyConstraint There is apparently no reason for RQLConstraint to inherit from RQLVocabularyConstraint as it gets its `repo_check` method from `RepoEnforcedRQLConstraintMixIn` and RQLVocabularyConstraint (which inherits from BaseRQLConstraint) actually only overrides that method. So simplify inheritance by removing a useless level of indirection. Adjust cw_unrelated_rql accordingly, where it was that RQLConstraint inherited from RQLVocabularyConstraint.

.. 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: tut_rql