useful for testing

When we configure LOGGING_ENABLED to DISABLED code does not
compile. Now it works!

Now if developers type "make help" they get a useful message.

The desired_accel is set again 11 lines lower so this line did nothing.

Simulated copter is flying too high and causing the land to timeout

Prevents possible loss of attitude reference for flights without optical flow and GPS.

The optical flow measurement timeout can reset the velocity states which decouples the position states from IMU errors and therefore significantly reduces the amount of attitude error correction.

don't use the 1kHz timer as it conflicts with other I2C devices