Add a "My Library" function

I would like to see a way to input cards that you own and the quantity of those cards so that it would be easier to build decks from your own library. I haven't looked into it yet but if trading is allowed you could give your friends access to your library to see if they would want to offer a trade. Also a nice tool would be to tell you if cards are already in a deck or not so you don't go looking through the heap forgetting it's already in use.
I should mention that I am new here so if this function already exists feel free to remove this post, or comment with the link. I sometimes over look things.