Add option to skip auto COM port search for Arduino

```
I have several dozens of COM ports installed by various Bluetooth adapters and 
devices, and scanning for a correct one (which is COM26) takes a lot of time 
and makes program unresponsive for this period.

```

Original issue reported on code.google.com by `positro...@gmail.com` on 25 Nov 2013 at 7:44
