Make ofSerial accessable

[GitBruno]

So we can check the connected devices before connecting. Or check if the device has been disconnected.
At the moment connected will always respond true after first connection.

// Check for disconnection and reconnect when plugged in again
if (deviceListLen != dmx.serial.getDeviceList().size()){
    dmx.disconnect();
};
if (!dmx.isConnected()) {
    dmx.connect(deviceID);
}