Additional payment, bank statement and voucher addons for OpenERP

Merge proposals dependent on lp://staging/~roberto-v/account-payment/adding_account_vat_on_payment_7

  1. adding_account_vat_on_payment_7
  2. Dependent merge proposals

lp://staging/~roberto-v/account-payment/adding_account_vat_on_payment_7 has no merge proposals.