This flag tells us if this item is by default assigned permanently (we
don't expect it to be returned back to inventory in some time interval
and therefore it is not declared missing after that time interval expires.
User has requirement to display items in some particular order, such as
drill 1 1/2", drill 1", drill 1/2", drill 3/4" and drill 3/8" should be
displayed as drill 3/8", drill 1/2", drill 3/4", drill 1" and drill 1 1/2".
List of selected subcategories.We need to store the entire categories in
here so that we have access to display order attribute to order the
categories correctly, therefore this list stores Category objects.