Merging GAM_LST script from bp/interp to aw/precip

Added script to evaluate climatic stationarity (Task #479)

Updates to run 12 months of mean daily precipitation using a variety of models. Includes using gamm() to incorporate spatial effects in addition to the smooth parameters. Not all clean and cozy yet, uploading as a work-in-progress...

Further updates to interpolation procedures including:

1) bugfix in MOD06_L2_data_compile. Root access is needed to run swtif in its current directory (bad design!).
2) Switched to UTM output from swtif (from sinusoidal) becuase it looked like gdal was struggling with integerized sinusoidal...

Modified GAM.R interpolation script to 1) simplify validation results, 2) add full prediction (rather than just stations) and 3) some other (hopefully) simplifications and improvements.

Updated GHCN_stations script to:

1) draw station location information from postgres database and perform merge/join query within database rather than r
2) add function to buffer region of interest to include stations outside region (to minimize edge effects)

Merging with bp/interp to use some of Benoit's code for precip interpolation

Merge branch 'bp/interp' into aw/precip

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