Pass accel calibration over telemetry stream. Telemetry data format change.

Pass accel calibration over telemetry stream. Telemetry data format change.

This allows the ground station to convert the accelerometer sensor
values into acceleration and speed data. This requires a new telemetry
data structure, and so TeleMetrum and TeleDongle units must be updated
synchronously. ao-view will parse either telemetry stream, and the
serial format from TeleDongle now has a version number to allow for
future changes.

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