DOC: StructureIndex macro documentation
add StructureIndex documentation to the manual: https://groupes.renater.fr/wiki/txm-users/public/macros#structureindex
(from redmine: issue id 2581, created on 2019/05/20 by Matthieu Decorde)
add StructureIndex documentation to the manual: https://groupes.renater.fr/wiki/txm-users/public/macros#structureindex
(from redmine: issue id 2581, created on 2019/05/20 by Matthieu Decorde)