Disabling encrypted preferences for export compliance

As I work on the Google Play release of the (installable broker) app, I'm required to agree that I've done all the important things for export compliance, particularly involving use of cryptography. All we use it for is for local encrypted preference saving, which is likely redundant with system permissions preventing other applications from reading preferences directly, so for simplicity and minimum lawyer involvement we should probably remove or at least ifdef-out the encryption use.