This is a work in progress. I am extending the "ExternalPipe" protocol to

This is a work in progress.  I am extending the "ExternalPipe" protocol to
have a "property" mode as well as the original "binary" mode.  The property mode
will allow the remote module to request any set of properties, and it will send
those properties each frame.  The remote module can reply with a list of arbitrary
property name/value pairs to update on the FlightGear side.

This is a first stab, so it's not the cleanest, most well concieved code, but it
allows an external module (communicating via a pipe) to have a huge amount of
flexibility in the data in can access and update.