Cleaned up the drop down field list creation function. Expanded some documentation.
Cleaned up the drop down field list creation function. Expanded some documentation.

ayan-usgs/PubsWarehouse_UI,jkreft-usgs/PubsWarehouse_UI,jkreft-usgs/PubsWarehouse_UI,USGS-CIDA/PubsWarehouse_UI,ayan-usgs/PubsWarehouse_UI,mbucknell/PubsWarehouse_UI,ayan-usgs/PubsWarehouse_UI,mbucknell/PubsWarehouse_UI,USGS-CIDA/PubsWarehouse_UI,ayan-usgs/PubsWarehouse_UI,mbucknell/PubsWarehouse_UI,USGS-CIDA/PubsWarehouse_UI,mbucknell/PubsWarehouse_UI,USGS-CIDA/PubsWarehouse_UI,jkreft-usgs/PubsWarehouse_UI,jkreft-usgs/PubsWarehouse_UI