QNL post harvest

[jacobthill]

QNL has mods data which is affected by the problem described in #285. However, in this case using the xml driver is not an option because we need the wait configuration and we don't have that option with the xml driver. We need to figure out the best way to harvest the data and once harvested appropriately, we need to address an issue with the post harvest task which causes empty array brackets to be written to the csv file when there is no data in the source record for a given element. e.g. we get [] in the csv columns which traject doesn't like.