Allow other modules modify what is logged on a transaction record

As a follow up to #2971697: Allow other modules modify the Realex Redirect data array , other modules can modify the data posted to Realex, so it is returned back to the site. However, it is then lost and inaccessible. We need to add in a drupal_alter() in commerce_realex_redirect_transaction_save() so custom variables are logged. Either that or we log all variables returned?