add crankshaft gwr_prediction infrastructure

src/pg/sql/29_gwr_predict.sql

@@ -0,0 +1,11 @@
+CREATE OR REPLACE FUNCTION
+CDB_GWR_PREDICT(subquery text, dep_var text, ind_vars text[],
+       bw numeric default null, fixed boolean default False, kernel text default 'bisquare')
+RETURNS table(coeffs JSON, stand_errs JSON, t_vals JSON, r_squared numeric, predicted numeric, rowid bigint)
+AS $$
+
+from crankshaft.regression import gwr_cs
+
+return gwr_cs.gwr_predict(subquery, dep_var, ind_vars, bw, fixed, kernel)
+
+$$ LANGUAGE plpythonu;