A simple packet sniffer. Listens to all packets received by the radio
and prints out the packets seen. 

This application requires that the SPOT it is on does not start up any
services that use the radio, e.g. OTA mode must be disabled.  It also
must be run on a SPOT, not as a host app, since it needs to access the
physical layer of the radio stack.

Note: while in promiscuous listening mode the radio chip will not send
out any ACKs, so any Spot sending us a packet will never be notified it
was delivered---the sender will get a No ACK exception.

Author: Ron Goldman
for the Orange release
