Javadoc
Returns true if this item can be added: it can be part of an object that is created.
In case of containers this means that the container itself should be displayed in creation forms
E.g. that the container label or block should be displayed. This usually happens if the container
contains at least one createable item.
This does NOT mean that also all the container items can be created. The sub-item permissions
are controlled by similar properties on the items. This property only applies to the container
itself: the "shell" of the container.