 By Lisandra Paraguassu BUENOS AIRES Reuters - Brazil and Argentina aim for greater economic integration, including the development of a common currency, Brazilian President Luiz Inacio Lula da Silva and Argentine leader Alberto Fernandez said in a joint article they penned. We intend to overcome the barriers to our exchanges, simplify and modernize the rules and encourage the use of local currencies, says the text published on the Argentine website Perfil. We also decided to advance discuss... 