the user should be notified of privacy policy changes

[cwillisf]

Prerequisites: #97, maybe #167

Expected Behavior

When the app can access the Internet, it should check for an updated privacy policy. If one is found, the app should notify the user and replace the built-in copy with the update.

Since this app is designed to support offline use, it is not an error for the privacy policy update check to fail. In that case the built-in privacy policy or the most recent successful update should be used.

Actual Behavior

Once #97 is resolved the app will be able to display a static privacy policy. We'll need to do more work to make that update dynamically.