6-point accelerometer calibration implemented
Added hysteresis to still detector
abs/fabs bugfix, logging cleanup
Merge branch 'master' into 6point_accel_calibration
Reset offsets/scales before calibration and use prescaled values in m/s^2 instead of raw values.
Still threshold increased to 0.1m/s^2, and orientation error threshold to 5m/s^2. Timeout increased to 30s.
Merge pull request #256 from rk3dov/6point_accel_calibration

6point accel calibration