dev #155235 Index thesaurus labels

* Cosmogramme / dynamic facets : add option to index thesaurus
labels. It indexes label terms in record **other text** field, each
term prefixed by the thesaurus code. Ex: HSUJE_JAPON HSUJE_TOKYO
* Search criteria **rech_thesaurus_** search only on terms prefixed
by the thesaurus code given. Ex: rech_thesaurus_SUJE/japon+tokyo
* In advanced search form, you can use a text element named
**rech_thesaurus_SUJE** to search on this specific thesaurus