Regional capabilities for precip variability

[acordonez]

• Subset grid by latitude and longitude - CropLatLon function and parser updates
• Add "standard" calendar checks
• Update filenames for arbitrary grid size
• Update RegridHoriz function for arbitrary lat/lon resolution
• Update Avg_PS_DomFrq to add custom region option
• Add option to crop dataset via shapefile
• Check for any remaining cdat reference to remove
• Clean up new code
• Resolve conflicts
• Document new features