this allows us to remove the display functions in the vehicle code,
and also allows us to store the format of a log file in the log. It
also stores the parameters used in a flight, rather than the
parameters set at the time the log is dumped
this will allow the addition of a DataFlash_File implementation of the
DataFlash API which will store logs in a traditional filesystem. That
will align better with the PX4 design, and be more useful for fast
transfer of logs to a host computer