altos: Split up flight code into separate flight/sample/kalman bits

The flight code mashed together data processing, filtering and actual
flight managament into one giant pile. Split things up so that we
have:

 ao_sample.c: Sensor data processing. Reads the ring, handles calibration
 ao_kalman.c: Filter the data to track the accel/speed/height values
 ao_flight.c: Flight state management, specific to rocketry.

The plan is to re-use ao_sample.c and ao_kalman.c for hardware not
specifically designed for rocketry, like TeleNano.

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