Add Delegate to ORSSerialPortManager

Add a delegate to ORSSerialPortManager.

The delegate has one required method `-(BOOL)ORSSerialPortManager:shouldAddSerialPort:` that allows the delegate to determine if the serial port should be managed within the application.

The delegate also contains two optional methods that mimic the notifications, but which allow the delegate's author to not manage interactions with the notification center.

The ORSSerialPort was expanded to include a reference to the IOKit device that the serial port is based off, so that this can be passed to the delegate, or inspected elsewhere for more information about the serial port.