soft delete gift cards

- adds is_deleted
- This way we have them for accounting purposes

Change-Id: Ibb89248d2eb8e46d0c5932e56567e5be5a304665
only show non-deleted gift cards in admin

- We dont currently have user views, but when we do
we should hide these from their views as well

Change-Id: Ief3ac58eb044c9c479a4edd83577febf0c7ccf83