Better align Orientation reference frames across platforms

[jkaufman]

Describe the bug
The reference frame for Orientation on iOS does not always match that on Android because React-Native-Sensors does not explicitly configure CoreMotion to return attitude readings relative to the ground plane and magnetic north.

Expected behavior
A consistent reference frame for Orientation values across platforms, or at least reference frames that both integrate gyroscope and magnetometer data.

Additional context
On Android, React-Native-Sensors pulls values from getOrientation() on SensorManager. According to the API docs, the reference frame is relative to magnetic north and gravity.

On iOS, React-native-Sensors pulls values from attitude from CMMotionManager.deviceMotion(). According to the API docs, the default reference frame is xArbitraryZVertical. However, CMMotionManager can be configured to use xMagneticNorthZVertical by passing it to startDeviceMotionUpdatesToQueue:… in RNSensorsOrientation.m (docs). Availability can be checked with isMagnetometerAvailable() or availableattitudereferenceframes(). While setting this reference frame requires a magnetometer, the same requirement applies to the current Android implementation of Orientation.

I'd be happy to submit a patch but wanted to get feedback on the proposal, first.

[jkaufman]

We migrated to expo-sensors, which accepted a patch to accomplish the same.