Create layer group for HUC and SPARROW output.

Layer groups: 

1. A layer group for HUCs
   1. name of layer group: Watershed Boundaries
   2. layers in the group: HUC2, HUC4, HUC8
2. A layer group for SPARROW output with new layers
   1. name of layer group: SPARROW 2002 Nutrient Model Results
   2. layers in the group: SPARROW 2002 Nitrogen Results, SPARROW 2002 Phosphorus Results

New Layers:

1. Name: SPARROW 2002 Nitrogen Results
   1. Geoserver id: gltg:sparrow-nitrogen
2. Name: SPARROW 2002 Phosphorus Results
   1. Geoserver id: gltg:sparrow-phosphorus