Automatic Serial Port Detection

Description: Ability to detect open serial ports and set the drop down menu in the Config tab to the available ports.
Demo: 
1. Run Mercury. Navigate to Config tab. Observe open ports in drop down menu.
2. Follow Demo 1, then open a new port. Observe the new port added to the list.
3. Follow Demo 1, then close an open port. Observe the port disappear from list.
