Add "Wishlist" concept to Mark As Visited

Some mechanism for ppl to keep a running list of places they want to go to will help keep their interest level high, faciliate planning ahead, and encourage them to visit. I envision them looking at our map, finding places of particular interest, marking them as "wishlist" / "want to visit" / "save for later" / "my saved list" / "bookmark" (exact working up to you), and being able to see a filtered view / list / icons of these places. Making the labels and icons customizable will be nice but also up to you.