Support touchstone file with more than 9 ports. (#935)

* Support touchstone file with more than 9 ports.

* Touchstone extension file can sometimes be upper case such as *.SP.

pyaedt/modeler/PrimitivesCircuit.py

@@ -335,7 +335,7 @@ def create_model_from_touchstone(self, touchstone_full_path, model_name=None):
             model_name = os.path.splitext(os.path.basename(touchstone_full_path))[0]
         if model_name in list(self.o_model_manager.GetNames()):
             model_name = generate_unique_name(model_name, n=2)
-        num_terminal = int(touchstone_full_path[-2:-1])
+        num_terminal = int(os.path.splitext(touchstone_full_path)[1].lower().strip(".sp"))
         with open(touchstone_full_path, "r") as f:
             port_names = _parse_ports_name(f)
         image_subcircuit_path = os.path.normpath(