Model results enhancement options

[jds485]

• finsh PDP plot targets (lower priority because SHAP dependence plots address this)
• Add other model performance metrics (NSE, KGE, Percent bias over all reaches)
• Spatial maps, barplots for other performance metrics
• Add a pred-obs and summary plots for only the training dataset
• Add confidence or prediction intervals for RF models (have keep.inbag = TRUE, so can plot this)
• Add reservoirs to spatial residual maps