IS_DISCONTINUED - excluded from search results

New KEYWORDS/tag search has discontinued condition.
Product page - ATC button hides if discontinued

If the product has the is tag IS_DISCONTINUED assigned, the add to cart
button container will be hidden and a message indicating item is not
available for purchase is added.
Add to cart preorder date check

If date in zoovy:prod_salesrank is found to be in the past, the preorder
skin will be removed from the add to cart button, and the standard add
to cart button will be shown.
handle preorder ship date check / version

Similar to add to cart for pre order items, if preorder date has past
today's date the "Will ship on %DATE%" message is not shown.
May need to present case for this same check to get shipping time quote
to run in getShipQuotes later on.