Correct behavior of unlimit quantity labels

When the `for` attribute of a label contains a non-unique value there is
no way to guarantee the label will associate itself with the correct
input. By using the ID associated with the wishlist item, a unique ID
can be used for each unlimited quantity checkbox.
Improve diplay of items with quantities

When someone wants more than one of something, but not an unlimited
amount, the quantity will now be displayed next to the item's name.

Also the claim button will only displayed for items that have an amount
left to claim. Note that claiming an item will cause it to appear to
others as if all of that item has been claimed even though the database
only reflects a claim of one.