[Feature Request] Block trader

It would be nice to have the option to blacklist traders, to prevent any future contact from them.

We have the option to add friends.  Sometimes you run across traders one may wish not to encounter again, for whatever reason (e.g., sent cards from wrong set or in non-near-mint condition, ignoring your profile).

It's not anything that would need to be included in the next release--just something I believe would be useful down the road.