Show speed. Format numbers. Timeout and report final status.

Show speed. Format numbers. Timeout and report final status.

The speed value is now shown in the top label bar. Ascent shows
accelerometer-derived data, otherwise it's baro derived.

All of the numbers displayed are now given sensible printf formats so they
don't contain way too many digits.

Instead of doing periodic reporting based on flight tick count, data is
reported every 10 seconds based on wall time. After landing, or when no data
have been received for a while, final flight information is spoken.

Signed-off-by: Keith Packard <keithp@keithp.com>