Separate logic for item sort order vs. category sort order

Our goal is to sort categories by the display sequence as defined in CX1, and sort items by best sellers.

Right now, we can only sort categories/sub-categories the same way we sort items. The admin setting for DEFAULT_NAVIGATION_SORT_BY controls both items and categories. Would be better if we had two separate settings so we can better control the sort orders separately for items and categories.