Show which cards are combo cards

[doctor-g]

The fact that a card was selected because of a combo is currently printed to the log but not present on the screen. It might be fun for a user to see which cards form combos, according to the data we have. There are two options I can think of:

1. Show which cards were selected because of the combo bias.
2. Show which cards have combos, regardless of whether this was a reason for their selection.

The first approach would require some additional tracking of why cards were chosen, whereas right now a card is simply either in the tableau or not. The second approach would be much easier because it can take advantage of the existing combo detection algorithm, but at the additional runtime cost of running each card through that filter before rendering them.