Added function that select either dummy or real VNA

Python_script/VNA.py

@@ -2,7 +2,13 @@
 
 import pyvisa
 import time
+from VNA_dummy import VnaDummy
 
+def create_VNA(hostname):
+    if hostname == 'localhost':
+        return VnaDummy(hostname)
+    else:
+        return Vna(hostname)
 
 class Vna:
     def __init__(self, ip_address):