General Bugfixes

Fixes:
 Fix for item description length - https://pagseguro.uol.com.br/v2/guia-de-integracao/api-de-pagamentos.html#v2-item-api-de-pagamentos-parametros-api
Fix for firecheckout, onepagecheckout  for ajax update requests (e.g shipping method changes)
Fix for ResponseJson  object null on firefox ajax return calls