Javadoc
Returns true if this item can be modified (updated).
In case of containers this means that the container itself should be displayed in modification forms
E.g. that the container label or block should be displayed. This usually happens if the container
contains at least one modifiable item.
This does NOT mean that also all the container items can be modified. 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.