Prepare code to be able to choose what to show into footer

htdocs/core/lib/pdf.lib.php

htdocs/core/modules/cheque/pdf/pdf_blochet.class.php

htdocs/core/modules/commande/doc/pdf_einstein.modules.php

htdocs/core/modules/commande/doc/pdf_proforma.modules.php

htdocs/core/modules/contract/doc/pdf_strato.modules.php

htdocs/core/modules/expedition/doc/pdf_rouget.modules.php

htdocs/core/modules/facture/doc/pdf_crabe.modules.php

htdocs/core/modules/fichinter/doc/pdf_soleil.modules.php

htdocs/core/modules/livraison/pdf/pdf_typhon.modules.php

htdocs/core/modules/project/pdf/pdf_baleine.modules.php

htdocs/core/modules/propale/doc/pdf_azur.modules.php

...core/modules/supplier_invoice/pdf/pdf_canelle.modules.php

.../core/modules/supplier_order/pdf/pdf_muscadet.modules.php

htdocs/langs/en_US/admin.lang