Continuous gyro bias estimation (#17)

Estimate gyro bias continuously instead of calibrating the gyro at startup.

flix/flix.ino

@@ -18,6 +18,7 @@ Vector gyro; // gyroscope data
 Vector acc; // accelerometer data, m/s/s
 Vector rates; // filtered angular rates, rad/s
 Quaternion attitude; // estimated attitude
+bool landed; // are we landed and stationary
 float motors[4]; // normalized motors thrust in range [-1..1]
 
 void setup() {