active scope on gift cards

exclude all gc's that have expired from the scope

Change-Id: I3a194611599f9fcde60902bcdeae68a7bc8344d1
spree::users_controller#gift_cards action

show all giftcards for the current user, add ?show_all to query string
to include expired giftcards as well.

Change-Id: I216afd6c32a07957363f7263f63f0006a259ef7d