Allow testing of Notifications

This just piggybacks a notification's data (for the moment just title, content and icon) on the `ShadowNotification`. This allows the data on the last sent Notification to be tested  by grabbing it from `ShadowNotificationManager.getNotification`.

Before this could only be tested if you were using the deprecated `Notification` constructor and then grabbed the data via `getLastEventInfo` which should no longer be used.