Change object default symbol in connect designer

The default symbol of objects is used for several things in ARIS, e.g. determination of the item type in content type config. At the moment it is only possible to change the default symbol either in the java client (properties/occurrences) or via a report script. It is necessary to add this functionality to set/change the objects default symbol, ideally in the 'Occurrences' tab in connect designer when the object is selected (either the definition in the repository, or an occurrence in a model).