This PR adds the features CPUserNotification and CPUserNotificationCenter in Foundation.
The CPUserNotificationCenter allows you to send user notification to the system.
Right now, we only propose what the W3C proposes. We can set for a notification the title, informativeText and the icon.
We only support local notification yet.
The protocol CPUserNotificationCenterDelegate has been added as well.
Test app in Tests/Manual/CPUserNotificationTest
