Add calibration data from near reference configuration.

This data is used to compute the reference pitch angle. This angle allows us to
calculate the lean rate.
Update calibration script to proto message.

In addition to the six configurations, this script now also computes the
reference pitch angle from data collect with zero steer, near zero lean, and
both wheels touching the ground.
Use MPU6050 calibration data in firmware.

This commit changes what MPU6050 data is stored.  The accelerometer and
gyroscope values are corrected using the respective sensitivity matrices and
bias vectors, and then transformed from the sensor frame to the lean frame. All
instances where gyroscope_y was used as the lean_rate have been updated.

The calculation of yaw_rate has also been updated to use the estimated lean
angle to transform from the lean frame to the yaw frame.  The yaw rate estimate
has been added to the estimate proto message.