Document calibration process

[Peque]

Specially to have a checklist before competitions.

1. Run calibrate_micrometers_per_count. It should run out of the starting cell, 3 more cells straight and stop at the last cell touching the front wall with the head. If the robot did not reach the target, decrease micrometers_per_count.
2. Run calibrate_wheels_separation. It should turn 4 times right. If the robot did not reach the target angle, increase wheels_separation.
3. Front sensors?
4. Side sensors?
5. Make sure the maze target (i.e.: the 0 distances) are right!
6. Make sure time delays for configuration/positioning are lenient.
7. Make sure the collision detection period (MAX_PWM_SATURATION_PERIOD) is high! i.e.: 0.5
8. DIAGONAL_MIN_DISTANCE