Change the default behavior of the Magnetometer on iOS to use geomagnetic values mode.

The current default iOS behavior uses the CMMagnetometer class in Core Motion that includes device bias. The bias there is not suitable for the calculations in general as it includes a static offset in the measurements that is caused by the device's magnetic field caused by its own components. To bring the iOS and Android default behavior in line, the default behavior of the magnetometer should be changed so that it would use the geomagnetic values mode.

Also, the name geomagnetic values mode should also be reviewed as it is not reflecting the naming used by the iOS API nor the actual behavior behind it (this mode has no effect on Android).