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>