#33 Event: entity reference for property changes
#33 Event: project entities must refer to their project
#33 Project reference ignored for JSON serialisation for all but for the branch
#33 Project reference can be repeated when registering an event
#33 Error handling at client side
#33 Event reference as a project entity type, not the entity itself
#33 Property event at client side
#33 Property icon for the event
#33 Property deletion event