Achievement to collect cards / view missing cards

[MephistoRoss]

When trying to collect all cards, it is currently not possible to see which cards you are still missing (unless you have enough gold to upgrade them all, so you can use the upgrade lvl 3 achievement to see which cards you are missing). Therefor it would be nice to add an achievement to collect cards so you can use the achievement to identify which cards you are missing. 

When new cards are added to the game, maybe reopen the achievement for players who already completed it but without a reward.

[Mynoduesp]

@MephistoRoss you can always use "copies<1" in the auction house.

Not a guarantee to have all cards listed there, but a solid workaround.

I'd like to add to the suggestions to track cards in statistics (as suggested here: https://forum.skylords.eu/index.php?/topic/9614-collection-information/) rather than an achievement which is kind of weird when it reopens upon expansion.