Rename module name to wifimgr

- Rename networkconfig.py to wifimgr.py 
- Update import module with new file name.

main.py

@@ -1,7 +1,7 @@
-import networkconfig
+import wifimgr
 
 
-wlan = networkconfig.get_connection()
+wlan = wifimgr.get_connection()
 if wlan is None:
     print("Could not initialize the network connection.")
     while True: