Fix add i18n behaviour in import export category loop
	modifié:         core/lib/Thelia/Core/Template/Loop/ImportExportCategory.php
Add description on tables
	modifié:         templates/backOffice/default/export-page.html
	modifié:         templates/backOffice/default/export.html
	modifié:         templates/backOffice/default/import.html