Serial Connection types should implement an interface

[ZiglioUK]

Classes such as NVSerialConnection and UBXSerialConnection should implement a common interface. That would make my life easier while building a GUI :-)

Methods such as

    public void init() throws Exception;
    public boolean isConnected() ;
    public static Vector getPortList(boolean showList);
    public void release(boolean waitForThread, long timeoutMs);
       ...

are common. Also, or alternatively, both classes should extend an abstract class in order to avoid code duplication.

[ZiglioUK]

Mmm, they already implement two different interfaces: StreamResource and StreamEventProducer, I'll see if I can do something with them without further changes