As a user I'd like to copy an existing item type to one or more other graphicyl elements.
Click the source element
If multiple items are attached to the source element, the user can select/deselect item types
click the target element
The item type is attached to the target element (item type of the same type mustn't exist on the target element)
This can e.g. be used as a backup function in case the element needs to change type (e.g. polygon --> grouped hole)
