Show detailed warning prior to deleting an object folder.

Our clients often try to select a couple of items in an object folder and then press the "delete" button. This used to trigger the default dependency message "There are dependencies, delete anyway?". 

Users often did not grasp that this actually deletes the whole folder (and not just the selected items).
So i have added a special case for folders, stating explicitly that the whole folder with its contents will be deleted.