Update existing resource with new files
Update existing resource with new files

When POSTing new files to /export/hydroshare?project=XX for
a project that has already been exported, we now update the
files for it in HydroShare and send back the updated Hydro-
ShareResource entity with an updated exported_at date.

WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed