Allow deletion when no references outside the nodes descendants

[colin-tactuum]

The DisableDeleteWhenReferenced setting is a great thing, but it would be good to have this turned on while allowing deletions where references are only within the children of the node you are trying to delete.

Parent node (has no references anywhere)

• Child 1 (has a reference to Child 2 & Child 3)
• Child 2 (has a reference to Child 4)
• Child 3 (has a reference to Child 4)
• Child 4 (has no references)

The current functionality will prevent you from deleting Parent node because descending items have dependencies. However, these dependencies are descendants of Parent node itself and would be deleted along with Parent node.