Add wishlists core app

A user can now add products to wishlists and manage them in her
account views. Specification is in #341
Wishlists: Keep title if product is deleted

Mirrors the behavior of OrderLines, keeping atleast the product title if
the product gets deleted.
Don't handle wish lists if user is not logged in
"Remove product" instead of "Delete product"

Seems like the better name.
Improve URLs and UX

URLs now have explicit keyword params, and removing from a wishlist can
be done now with either the product's or line's PK.
The UX for the 'Add to wish list' button has been improved. Please just
look at it ;)
Enforce name-giving when creating wish list
Notification and template tweaks
Make wishlist forms overridable