Merge branch 'feature-11-notification-area' into feature-3-refactoring-properties
refactoring Validation result: now a validation result uses notifications internally
notifications can calculate now the dominant color of an icon and use this as default notificatoin color
refactoring
lightened up the frame
added validation state "necessary field"
added test showing the possibility to use an own notification
improved error messages
Merge branch 'feature-3-refactoring-properties' into feature-11-notification-area
a single notification can be shown multiple times