Merge branch 'robsonek-patch-1'

Merge branch 'v5'

changed Accept header for GetParcelLabelRequestV1.php and GetParcelsP…

…rotocolRequestV1.php

info about v6.x

added new size table requests:

allegro/allegro-api#4888

added Accept-Language header to RequestTrait.php

added lineItemsSent param to PutCheckoutFormFulfillmentRequestV1.php

another bugfix for the same resource

bugfix for PutCheckoutFormInvoiceFileRequestV1.php

added new resources

allegro/allegro-api#4586