More format choices and better file extensions for Gobi open order status reports

Gobi sends us open order status reports with an attachment that ends ".dat". That has no meaning at all to anyone's desktop software and just causes problems. Further, the most common format usable for this kind of data is NOT offered as an option, and that's tab delimited. So this idea is two parts: add tab-delimited as an option for receiving those reports AND when that option is selected, use the .tsv file extension for them.