Create notification explanation UI

[adamwolf]

Android 34 wants us to create some popup UI:

                // TODO: display an educational UI explaining to the user the features that will be enabled
                //       by them granting the POST_NOTIFICATION permission. This UI should provide the user
                //       "OK" and "No thanks" buttons. If the user selects "OK," directly request the permission.
                //       If the user selects "No thanks," allow the user to continue without notifications.