Add overlay product layer, to hold the following overlay products:

- Storm Structure (NSS/62)
- Hail Index (NHI/59)
- Mesocyclone (NME/60, NMD/141)
- Tornadic Vortex Signature (NTV/61)
- Storm Tracking Information (NST/58)

scwx-qt/source/scwx/qt/model/layer_model.cpp

@@ -43,6 +43,7 @@ static const std::vector<types::LayerInfo> kDefaultLayers_ {
     types::InformationLayer::RadarSite,
     false,
     {false, false, false, false}},
+   {types::LayerType::Data, types::DataLayer::OverlayProduct, true},
    {types::LayerType::Data, types::DataLayer::RadarRange, true},
    {types::LayerType::Alert, awips::Phenomenon::Tornado, true},
    {types::LayerType::Alert, awips::Phenomenon::SnowSquall, true},