Add a wishlist feature

[russback]

What are you trying to do?
It would be useful to be able to have a list that is equivalent to a cart that can be shared with other people. Typically items can be moved from cart to wishlist and vice versa.

There is a third party plugin which does a good job but it feels that given a wishlist is essentially a cart with less functionality, it would make sense to have it as a core feature.