Rename, reorder Shippensburg layers
Rename, reorder Shippensburg layers

The `helptext` field didn't feel very helpful, only repetitive,
so I removed it.

Refs #2889

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