simplify mobiledevice.c -> rename to mobiledevice.m and use NSSttring instead of CFString and ARC

saves about 100 lines of code and makes string deallocation a bit more safe 
I want to avoid ```?``` one liners as much as possible so, I would see this code as:

```objc
if (udid == nil)
{
  unregister_device_notification(1);
}
else
{
  printfNS(@"%@\n", udid);
  unregister_device_notification(0);
}
```