Output warning if starting heat price is greater than ending heat pri…

…ce (issue 254)

src/geophires_x/Economics.py

@@ -2148,6 +2148,11 @@ def read_parameters(self, model: Model) -> None:
                                                      " range 0-10. GEOPHIRES will assume default surface plant O&M cost correlation with" +
                                                      " adjustment factor = 1.")
                                 ParameterToModify.value = 1.0
+            if self.HeatStartPrice.value > self.HeatEndPrice.value:
+                s = f'{self.HeatStartPrice.Name} cannot be greater than {self.HeatEndPrice.Name}.  ' \
+                    f'GEOPHIRES will assume {self.HeatStartPrice.Name} is equal to {self.HeatEndPrice.Name}.'
+                print("Warning:  " + s)
+                model.logger.warning(s)
         else:
             model.logger.info("No parameters read because no content provided")