Add import description
	modifié:         core/lib/Thelia/Config/Resources/import.xml
	modifié:         core/lib/Thelia/ImportExport/Import/Type/ProductStockImport.php
	modifié:         templates/backOffice/default/ajax/export-modal.html
	modifié:         templates/backOffice/default/ajax/import-modal.html
	modifié:         templates/backOffice/default/export-page.html
	modifié:         templates/backOffice/default/export.html
	modifié:         templates/backOffice/default/import-page.html
	modifié:         templates/backOffice/default/import.html