OR data preparation, initial commit for extraction of covariates from raster stack

OR data preparation task#363, modified code for ghcn to create a shapefile

GHNCD station data selection using Postgres database, initial commit, task #363

GAM LST, added specific and general diagnostic measures (e.g.MAE) GAM+Kriging, task #364 and #406

GAM LST, adding lines to summarize samling RMSE using plots, task #409

GAM LST, first code to test effect of sampling on GAM, task #409

GAM LST, added model and modified summary plots, run on 365 dates GAM+Kriging, task #364 and #406

GAM LST, modify code to generalize number of models and assessment,GAM+Kriging task #364

GAM LST, major modifications to create GAM+Kriging code, task #364

GAM LST, adding lines to assess RMSE per month over 365 dates, task #406