Add binding for pcap Send

Updates completed as per your comments on the previous pull request.
I also changed the example to match the change to ThrowException in the send method.

FWIW, my issue with >60 second spool up was in pcap_findalldevs. My system was hanging when iterating through the USB driver for interfaces!  Nothing to do with our code. tcpdump was showing the same behaviour when no interface was specified.
Yeah, if they only provide a Buffer and no length argument, default to the Buffer length. If they do provide a second argument, we want to make sure it is an unsigned integer though.