Here is a big one with the WaterML parser and hooking it up

All we should need to do yet is mux all the connectors together.
This isn't quite correct anymore but I think the logic is in the wrong place anyway. The way the download form sends parameters makes it so we have all parameters available at all times, even when some parameters don't apply. 

My original intent was to make sure we DON'T ask for any constituents other than Q for the annual/daily flow downloads.

However, the SosAggregationService really should not have this logic and should aggregate/mux whatever it sees. I think we have to adjust incoming parameters at the Webservice layer (DownloadService) to make sure only applicable options are applied for each unique download type.