Added a device name option in Touch.Server/Main.cs

Hi Sebastien,

I have included a device name parameter in var os in Touch.Server/Main.cs.  This will allow users to pass device name to Touch.Unit. This makes the user execute test in multiple devices attached to a mac. Previously, if multiple devices are attached, tests used to execute that many times in a single device. 

Please verify. It would be great if you could also include this in your Touch.Unit repo

Best,
Gouri