bin/GetCatchmentShapefileForNHDStreamflowGage.py: Added option to
query from web service (the default)

bin/GetNHDStreamflowGageIdentifiersAndLocation.py: Added option to
query from web service (the default)

ecohydrolib/nhdplus2/webservice.py: Updated
getCatchmentFeaturesForStreamflowGage to return tuple of filename and
URL, instead of just filename

ecohydrolib/tests/test_nhdwebsvc.py: Updated to support minor changes to API

bin/GetNLCDForDEMExtent.py: Changed default from local to wcs
Moved several constants used for talking to OGR into spatialdata.util.
Forgot to include in previous commit.
- Changes in file mode, removing unnecessary execute bit
Updated to include NHDPlusV2 CGIs