Detect side changes

Test out whether it is possible to use the magnetometer or gyroscope to automatically detect which side the user is on after they start the app:

1. When the user starts the app by specifying which side they're on, capture which direction the user is facing by reading the magnetometer or gyroscope
2. If the user switches sides, the direction they're facing should be opposite to the one captured, so if this occurs, then Sideways Mode should automatically switch side instead of requiring the user to manually specify the new side