Merge branch '1317-documenter-les-impressions' into next_version

doc/source/administrator/impression/impressions.md

doc/source/administrator/index.rst

...or/impressions/ajouter_outil_impression_dans_la_carte.png

doc/source/images/administrator/impressions/echelles.png

.../administrator/impressions/exemple-boucle-map-legende.png

doc/source/images/administrator/impressions/html_logo.png

...mages/administrator/impressions/icon_outil_impression.png

...rce/images/administrator/impressions/mode_impressions.png

...trator/impressions/selection_du_style_des_impressions.png