Final fix for issue #66 - new lines had to be escaed in CUSTOM_DATA sub values.
Fix Issue #60: 409 return codes are not considered as errors anymore. Report is considered as already received and is discarded.
Issue #60: when a ReportSender fails to send ONE report, it was blocking all other reports from being sent. Now we allow other reports to be processed. If the error was due to a temporary server-side outage, there's no real fear to be overloaded, each app can only send 5 reports on each sending session.