Added 3 new models and nesting to GAM, task #361

Changes in the diagnostics plots, barplots.

Transform aspect in Eastness and Northness variables in the GAM.

Transformed the aspect variable and added GAM model closer to PRISM

GAM prediction added to the loop with RMSE calculation

Streamlining and slight changes to the loop to create subset dataset for different dates

Additional changes to the loop and format

Start of Task #361, modified code to subset for 10 dates

Minor format changes and clean up to code

Corrected errors in RMSE calculation and added plots to view results