Accept different formats of SRS

[emlys]

Pygeoprocessing functions that take in a SRS parameter require it to be in WKT format. GDAL/OGR utilities also accept EPSG and ESRI codes, PROJ strings, and more. We usually define projections in terms of EPSG codes anyway, so it would be convenient to pass those directly to pygeoprocessing. It's also nice to be consistent with GDAL when possible.

From the ogr2ogr docs, srs parameters may be

anything supported by the OGRSpatialReference.SetFromUserInput() call, which includes EPSG Projected, Geographic or Compound CRS (i.e. EPSG:4296), a well known text (WKT) CRS definition, PROJ.4 declarations, or the name of a .prj file containing a WKT CRS definition.

From a quick search, functions that take WKT parameters are

• align_and_resize_raster_stack
• create_raster_from_bounding_box
• reproject_vector
• warp_raster
• transform_bounding_box
• shapely_geometry_to_vector
• numpy_array_to_raster