Allow disabling sound on notifications

Test local notifications Install the app in a device (test this both in Android and iOS). Schedule a local notification (calendar event) to be triggered soon, put the app in background and wait for it to trigger. Check that a sound is played when it's triggered.  Resume the app and schedule another local notification. Before it triggers, go to App Settings > Notification preferences and disable "Play sound". Put the app in background and wait for it to trigger. Check that a sound is NOT played when it's triggered. Test push notifications Install the app in a device (Android only, since push notifications are hard to test in iOS). Go to App Settings > Notification preferences and check that "Play sound" is enabled. Put the app in background and send a push notification to the app (e.g. send a message to the user). Check that a sound is played when the notification is shown. Resume the app, go to App Settings > Notification preferences and disable "Play sound". Perform step 3 again but check that now the sound isn't played.