- bin/GetNLCDForDEMExtent.py: Added ability download NLCD data from
  webmap.ornl.gov via WCS
- ecohydrolib/nlcd/daacquery.py: Created to support WCS download of NLCD
- ecohydrolib/wcs4dem/demquery.py: Refactored WCS code into generic library
  function
- ecohydrolib/wcslib.py: Created generic library function for WCS download
  of raster