Bug/discovery full udp buffer

[momoAmch]

lease refer to this issue for further information #377

Add an option to configure the UDP receive buffer size as an option on probe function
Use setImmediate inside the 'message' listener to defer heavy parsing to the next event loop phase.

[RogerHardiman]

Many thanks for the changes.
Testing it now.

Thanks for the useAddr addition.
And thank you for spotting what looks like a race condition where the Discovery message is not waiting for Bind() to complete.
I like the SetImmediate() to move the XML processing off the main event loop.

My only comment was the option to increase the buffer size.
Perhaps we should always increase the buffer size.