Issue #838

The solution I propose for #838 is as follows:

Data downloads happen from the layer that is linked as the 'WFS Layer'. If the data should come from the same layer as the map does then the map layer should be linked as its own WFS Layer. If no WFS Layer is linked to a WMS Layer then the 'Download as CSV' option is not displayed to the users.

If there is a URL download column configured for the layer then the 'Download as list of URLs' and 'Download source NetCDF files' options will be available. This is independent of whether there is a CSV download option.

When AODAAC is ready then if there is a linked AODAAC product then the download will be of that product. Until we have AODAAC integration the URL list download option will be displayed.