New: Can use extrafields on third parties.

ChangeLog

htdocs/adherents/admin/adherent_extrafields.php

htdocs/adherents/class/adherent.class.php

htdocs/adherents/fiche.php

htdocs/admin/societe.php

htdocs/admin/societe_extrafields.php

htdocs/core/class/extrafields.class.php

htdocs/lib/company.lib.php

htdocs/lib/member.lib.php

htdocs/societe/class/societe.class.php

htdocs/societe/soc.php